diff --git a/tools/lib/capitalization.py b/tools/lib/capitalization.py
index 02c064b5e8..1fd4a6077a 100644
--- a/tools/lib/capitalization.py
+++ b/tools/lib/capitalization.py
@@ -140,6 +140,10 @@ IGNORED_PHRASES = [
     r"does not apply to moderators and administrators",
     # Used in message-delete-time-limit setting label
     r"does not apply to administrators",
+    # Used as indicator with names for guest users.
+    r"guest",
+    # Used in pills for deactivated users.
+    r"deactivated",
 ]
 
 # Sort regexes in descending order of their lengths. As a result, the
diff --git a/web/src/buddy_data.js b/web/src/buddy_data.js
index 5759c14a5b..6137578f1e 100644
--- a/web/src/buddy_data.js
+++ b/web/src/buddy_data.js
@@ -152,6 +152,7 @@ export function info_for(user_id) {
         user_circle_class,
         status_text,
         user_list_style,
+        should_add_guest_user_indicator: people.should_add_guest_user_indicator(user_id),
     };
 }
 
diff --git a/web/src/compose_validate.js b/web/src/compose_validate.js
index 2550febdee..43f7ef0315 100644
--- a/web/src/compose_validate.js
+++ b/web/src/compose_validate.js
@@ -173,6 +173,7 @@ export function warn_if_mentioning_unsubscribed_user(mentioned, $textarea) {
                 can_subscribe_other_users,
                 name: mentioned.full_name,
                 classname: compose_banner.CLASSNAMES.recipient_not_subscribed,
+                should_add_guest_user_indicator: people.should_add_guest_user_indicator(user_id),
             };
 
             const new_row = render_not_subscribed_warning(context);
diff --git a/web/src/input_pill.ts b/web/src/input_pill.ts
index 9fa5e29643..5184fc2821 100644
--- a/web/src/input_pill.ts
+++ b/web/src/input_pill.ts
@@ -17,6 +17,7 @@ export type InputPillItem<T> = {
     img_src?: string;
     deactivated?: boolean;
     status_emoji_info?: EmojiRenderingDetails & {emoji_alt_code: boolean}; // TODO: Move this in user_status.js
+    should_add_guest_user_indicator?: boolean;
 } & T;
 
 type InputPillCreateOptions<T> = {
@@ -55,6 +56,7 @@ type InputPillRenderingDetails = {
     deactivated?: boolean;
     has_status?: boolean;
     status_emoji_info?: EmojiRenderingDetails & {emoji_alt_code: boolean};
+    should_add_guest_user_indicator?: boolean;
 };
 
 // These are the functions that are exposed to other modules.
@@ -156,6 +158,7 @@ export function create<T>(opts: InputPillCreateOptions<T>): InputPillContainer<T
                 display_value: item.display_value,
                 has_image,
                 deactivated: item.deactivated,
+                should_add_guest_user_indicator: item.should_add_guest_user_indicator,
             };
 
             if (has_image) {
diff --git a/web/src/message_list_view.js b/web/src/message_list_view.js
index 7b4efa369a..b33c50ac49 100644
--- a/web/src/message_list_view.js
+++ b/web/src/message_list_view.js
@@ -418,6 +418,8 @@ export class MessageListView {
 
         message_container.sender_is_bot = people.sender_is_bot(message_container.msg);
         message_container.sender_is_guest = people.sender_is_guest(message_container.msg);
+        message_container.should_add_guest_indicator_for_sender =
+            people.should_add_guest_user_indicator(message_container.msg.sender_id);
 
         message_container.small_avatar_url = people.small_avatar_url(message_container.msg);
         if (message_container.msg.stream_id) {
diff --git a/web/src/page_params.ts b/web/src/page_params.ts
index 70749a98e8..2042aed8e3 100644
--- a/web/src/page_params.ts
+++ b/web/src/page_params.ts
@@ -68,6 +68,7 @@ export const page_params: {
     realm_private_message_policy: number;
     realm_push_notifications_enabled: boolean;
     realm_sentry_key: string | undefined;
+    realm_enable_guest_user_indicator: boolean;
     realm_upload_quota_mib: number | null;
     realm_uri: string;
     realm_user_group_edit_policy: number;
diff --git a/web/src/people.ts b/web/src/people.ts
index 74c8b69576..0fbc78bf48 100644
--- a/web/src/people.ts
+++ b/web/src/people.ts
@@ -770,6 +770,15 @@ export function user_is_bot(user_id: number): boolean {
     return user.is_bot;
 }
 
+export function should_add_guest_user_indicator(user_id: number): boolean {
+    if (!page_params.realm_enable_guest_user_indicator) {
+        return false;
+    }
+
+    const user = get_by_user_id(user_id);
+    return user.is_guest;
+}
+
 export function user_can_direct_message(recipient_ids_string: string): boolean {
     // Common function for checking if a user can send a direct
     // message to the target user (or group of users) represented by a
diff --git a/web/src/search_suggestion.js b/web/src/search_suggestion.js
index 0abd25635e..a83c7acf53 100644
--- a/web/src/search_suggestion.js
+++ b/web/src/search_suggestion.js
@@ -34,6 +34,7 @@ function highlight_person(person, highlighter) {
         display_value: new Handlebars.SafeString(highlighted_name),
         has_image: true,
         img_src: avatar_url,
+        should_add_guest_user_indicator: people.should_add_guest_user_indicator(person.user_id),
     };
 }
 
diff --git a/web/src/typeahead_helper.js b/web/src/typeahead_helper.js
index 065163d223..cdc9b6da27 100644
--- a/web/src/typeahead_helper.js
+++ b/web/src/typeahead_helper.js
@@ -92,6 +92,7 @@ export function render_person(person) {
         user_circle_class,
         is_person: true,
         status_emoji_info,
+        should_add_guest_user_indicator: people.should_add_guest_user_indicator(person.user_id),
     };
 
     typeahead_arguments.secondary = person.delivery_email;
diff --git a/web/src/user_card_popover.js b/web/src/user_card_popover.js
index f09f433787..9dbca15c53 100644
--- a/web/src/user_card_popover.js
+++ b/web/src/user_card_popover.js
@@ -289,6 +289,7 @@ function get_user_card_popover_data(
         user_mention_syntax: people.get_mention_syntax(user.full_name, user.user_id),
         date_joined,
         spectator_view,
+        should_add_guest_user_indicator: people.should_add_guest_user_indicator(user.user_id),
     };
 
     if (user.is_bot) {
diff --git a/web/src/user_pill.js b/web/src/user_pill.js
index a4ea3977bc..9bf608f86a 100644
--- a/web/src/user_pill.js
+++ b/web/src/user_pill.js
@@ -53,12 +53,12 @@ export function create_item_from_email(email, current_items) {
         img_src: avatar_url,
         deactivated: false,
         status_emoji_info,
+        should_add_guest_user_indicator: people.should_add_guest_user_indicator(user.user_id),
     };
 
     // We pass deactivated true for a deactivated user
     if (!people.is_person_active(user.user_id)) {
         item.deactivated = true;
-        item.display_value = user.full_name + " (deactivated)";
     }
 
     return item;
@@ -81,6 +81,7 @@ export function append_person(opts) {
         email: person.email,
         img_src: avatar_url,
         status_emoji_info,
+        should_add_guest_user_indicator: people.should_add_guest_user_indicator(person.user_id),
     };
 
     pill_widget.appendValidatedData(pill_data);
diff --git a/web/src/user_profile.js b/web/src/user_profile.js
index 96d77e53af..181b64bd04 100644
--- a/web/src/user_profile.js
+++ b/web/src/user_profile.js
@@ -366,6 +366,7 @@ export function show_user_profile(user, default_tab_key = "profile-tab") {
         user_is_guest: user.is_guest,
         show_user_subscribe_widget,
         can_manage_profile,
+        should_add_guest_user_indicator: people.should_add_guest_user_indicator(user.user_id),
     };
 
     if (user.is_bot) {
diff --git a/web/styles/popovers.css b/web/styles/popovers.css
index e3b043f802..2342dca6d0 100644
--- a/web/styles/popovers.css
+++ b/web/styles/popovers.css
@@ -223,7 +223,7 @@ ul {
         display: inline-block;
         text-align: center;
 
-        &:not(.popover_action_icon) {
+        &:not(.popover_action_icon, .guest-indicator) {
             width: 14px;
         }
 
diff --git a/web/templates/compose_banner/not_subscribed_warning.hbs b/web/templates/compose_banner/not_subscribed_warning.hbs
index a809195bd1..7a11fc0323 100644
--- a/web/templates/compose_banner/not_subscribed_warning.hbs
+++ b/web/templates/compose_banner/not_subscribed_warning.hbs
@@ -1,9 +1,17 @@
 {{#> compose_banner }}
     <p class="banner_message">
         {{#if can_subscribe_other_users}}
+            {{#if should_add_guest_user_indicator}}
+            {{#tr}}<strong>{name}</strong> <i>(guest)</i> is not subscribed to this stream. They will not be notified unless you subscribe them.{{/tr}}
+            {{else}}
             {{#tr}}<strong>{name}</strong> is not subscribed to this stream. They will not be notified unless you subscribe them.{{/tr}}
+            {{/if}}
         {{else}}
+            {{#if should_add_guest_user_indicator}}
+            {{#tr}}<strong>{name}</strong> <i>(guest)</i> is not subscribed to this stream. They will not be notified if you mention them.{{/tr}}
+            {{else}}
             {{#tr}}<strong>{name}</strong> is not subscribed to this stream. They will not be notified if you mention them.{{/tr}}
+            {{/if}}
         {{/if}}
     </p>
 {{/compose_banner}}
diff --git a/web/templates/input_pill.hbs b/web/templates/input_pill.hbs
index 53bc1520c4..2dfb00256d 100644
--- a/web/templates/input_pill.hbs
+++ b/web/templates/input_pill.hbs
@@ -4,6 +4,8 @@
     {{/if}}
     <span class="pill-label">
         <span class="pill-value">{{ display_value }}</span>
+        {{~#if should_add_guest_user_indicator}}&nbsp;<i>({{t 'guest'}})</i>{{~/if~}}
+        {{~#if deactivated}}&nbsp;({{t 'deactivated'}}){{~/if~}}
         {{~#if has_status~}}
             {{~> status_emoji status_emoji_info~}}
         {{~/if~}}
diff --git a/web/templates/message_body.hbs b/web/templates/message_body.hbs
index f1ecfe2eaa..14f520f5ad 100644
--- a/web/templates/message_body.hbs
+++ b/web/templates/message_body.hbs
@@ -5,7 +5,7 @@
     {{#if include_sender}}
         <span class="sender_info_hover sender_name" role="button" tabindex="0">
             <span class="view_user_card_tooltip sender_name_text" data-tooltip-template-id="view-user-card-tooltip-template">
-                {{msg/sender_full_name}}
+                {{> user_full_name name=msg/sender_full_name should_add_guest_user_indicator=should_add_guest_indicator_for_sender}}
             </span>
             {{#unless status_message}}
             {{> status_emoji msg/status_emoji_info}}
diff --git a/web/templates/popovers/user_card/user_card_popover.hbs b/web/templates/popovers/user_card/user_card_popover.hbs
index 954504cf56..fdeeafd833 100644
--- a/web/templates/popovers/user_card/user_card_popover.hbs
+++ b/web/templates/popovers/user_card/user_card_popover.hbs
@@ -3,7 +3,7 @@
 <div class="user-card-popover-content no-auto-hide-right-sidebar-overlay">
     <ul class="nav nav-list user-card-popover-actions" id="user_card_popover" data-user-id="{{user_id}}">
         <li class="popover_user_name_row">
-            <b class="user_full_name" data-tippy-content="{{user_full_name}}">{{user_full_name}}</b>
+            <b class="user_full_name" data-tippy-content="{{user_full_name}}">{{> ../../user_full_name name=user_full_name}}</b>
             {{#if is_active }}
                 {{#if is_bot}}
                 <i class="zulip-icon zulip-icon-bot" aria-hidden="true"></i>
diff --git a/web/templates/presence_row.hbs b/web/templates/presence_row.hbs
index 690e321df7..a8ca9e2ff7 100644
--- a/web/templates/presence_row.hbs
+++ b/web/templates/presence_row.hbs
@@ -8,13 +8,13 @@
             {{#if user_list_style.WITH_STATUS}}
                 <div class="user-name-and-status-wrapper">
                     <div class="user-name-and-status-emoji">
-                        <span class="user-name">{{name}}</span>
+                        <span class="user-name">{{> user_full_name}}</span>
                         {{> status_emoji status_emoji_info}}
                     </div>
                     <span class="status-text">{{status_text}}</span>
                 </div>
             {{else}}
-                <span class="user-name">{{name}}</span>
+                {{> user_full_name}}
                 {{> status_emoji status_emoji_info}}
             {{/if}}
         </a>
diff --git a/web/templates/typeahead_list_item.hbs b/web/templates/typeahead_list_item.hbs
index 49fb2f21c2..e4a7f542c8 100644
--- a/web/templates/typeahead_list_item.hbs
+++ b/web/templates/typeahead_list_item.hbs
@@ -24,6 +24,9 @@
         {{~ primary ~}}
     {{/if}}
 </strong>
+{{~#if should_add_guest_user_indicator}}
+    <i>({{t 'guest'}})</i>
+{{~/if}}
 {{~#if has_status}}
 {{> status_emoji status_emoji_info}}
 {{~/if}}
diff --git a/web/templates/user_full_name.hbs b/web/templates/user_full_name.hbs
new file mode 100644
index 0000000000..8103610f43
--- /dev/null
+++ b/web/templates/user_full_name.hbs
@@ -0,0 +1,5 @@
+{{#if should_add_guest_user_indicator}}
+{{#tr}}{name} <i class="guest-indicator">(guest)</i>{{/tr}}
+{{else}}
+<span class="user-name">{{name}}</span>
+{{/if}}
diff --git a/web/templates/user_profile_modal.hbs b/web/templates/user_profile_modal.hbs
index 4677d86419..dafc8a50d8 100644
--- a/web/templates/user_profile_modal.hbs
+++ b/web/templates/user_profile_modal.hbs
@@ -11,7 +11,7 @@
                     {{#if is_bot}}
                         <i class="zulip-icon zulip-icon-bot" aria-hidden="true"></i>
                     {{/if}}
-                    <span class="user_profile_name">{{full_name}}</span>
+                    <span class="user_profile_name">{{> user_full_name name=full_name}}</span>
                     {{#if is_me}}
                         <a href="/#settings/profile">
                             <i class="fa fa-edit tippy-zulip-tooltip user_profile_manage_own_edit_button" data-tippy-content="{{t 'Edit profile' }}" aria-hidden="true"></i>
diff --git a/web/tests/activity.test.js b/web/tests/activity.test.js
index 4ed8fab250..6577c267ef 100644
--- a/web/tests/activity.test.js
+++ b/web/tests/activity.test.js
@@ -400,6 +400,7 @@ test("first/prev/next", ({override, mock_template}) => {
                         WITH_STATUS: true,
                         WITH_AVATAR: false,
                     },
+                    should_add_guest_user_indicator: false,
                 });
                 break;
             case fred.user_id:
@@ -419,6 +420,7 @@ test("first/prev/next", ({override, mock_template}) => {
                         WITH_STATUS: true,
                         WITH_AVATAR: false,
                     },
+                    should_add_guest_user_indicator: false,
                 });
                 break;
             /* istanbul ignore next */
@@ -489,6 +491,7 @@ test("insert_one_user_into_empty_list", ({override, mock_template}) => {
                 WITH_STATUS: true,
                 WITH_AVATAR: false,
             },
+            should_add_guest_user_indicator: false,
         });
         assert.ok(html.startsWith("<li data-user-id="));
         return html;
diff --git a/web/tests/buddy_data.test.js b/web/tests/buddy_data.test.js
index e11522d6dc..db754bac03 100644
--- a/web/tests/buddy_data.test.js
+++ b/web/tests/buddy_data.test.js
@@ -519,6 +519,7 @@ test("get_items_for_users", () => {
             user_circle_class: "user_circle_green",
             user_id: 1001,
             user_list_style,
+            should_add_guest_user_indicator: false,
         },
         {
             faded: false,
@@ -531,6 +532,7 @@ test("get_items_for_users", () => {
             user_circle_class: "user_circle_empty",
             user_id: 1002,
             user_list_style,
+            should_add_guest_user_indicator: false,
         },
         {
             faded: false,
@@ -543,6 +545,7 @@ test("get_items_for_users", () => {
             user_circle_class: "user_circle_empty",
             user_id: 1003,
             user_list_style,
+            should_add_guest_user_indicator: false,
         },
     ]);
 });
diff --git a/web/tests/compose_pm_pill.test.js b/web/tests/compose_pm_pill.test.js
index 802af767c2..1522faa367 100644
--- a/web/tests/compose_pm_pill.test.js
+++ b/web/tests/compose_pm_pill.test.js
@@ -124,7 +124,7 @@ run_test("pills", ({override, override_rewire}) => {
             assert.ok(get_by_email_called);
             assert.equal(typeof res, "object");
             assert.equal(res.user_id, iago.user_id);
-            assert.equal(res.display_value, iago.full_name + " (deactivated)");
+            assert.equal(res.display_value, iago.full_name);
             assert.ok(res.deactivated);
             people.add_active_user(iago);
         })();
diff --git a/web/tests/message_list_view.test.js b/web/tests/message_list_view.test.js
index 5836f42ff0..9db8bd3a17 100644
--- a/web/tests/message_list_view.test.js
+++ b/web/tests/message_list_view.test.js
@@ -37,6 +37,7 @@ mock_esm("../src/rows", {
 mock_esm("../src/people", {
     sender_is_bot: () => false,
     sender_is_guest: () => false,
+    should_add_guest_user_indicator: () => false,
     small_avatar_url: () => "fake/small/avatar/url",
 });
 
diff --git a/web/tests/people.test.js b/web/tests/people.test.js
index 525de113d7..f3242bdb04 100644
--- a/web/tests/people.test.js
+++ b/web/tests/people.test.js
@@ -1276,6 +1276,19 @@ test_people("get_realm_active_human_users", () => {
     assert.deepEqual(humans, [me]);
 });
 
+test_people("should_show_guest_user_indicator", () => {
+    people.add_active_user(charles);
+    people.add_active_user(guest);
+
+    page_params.realm_enable_guest_user_indicator = false;
+    assert.equal(people.should_add_guest_user_indicator(charles.user_id), false);
+    assert.equal(people.should_add_guest_user_indicator(guest.user_id), false);
+
+    page_params.realm_enable_guest_user_indicator = true;
+    assert.equal(people.should_add_guest_user_indicator(charles.user_id), false);
+    assert.equal(people.should_add_guest_user_indicator(guest.user_id), true);
+});
+
 // reset to native Date()
 run_test("reset MockDate", () => {
     MockDate.reset();
diff --git a/web/tests/search_suggestion.test.js b/web/tests/search_suggestion.test.js
index 44d28c5b2a..f91b679846 100644
--- a/web/tests/search_suggestion.test.js
+++ b/web/tests/search_suggestion.test.js
@@ -853,6 +853,7 @@ test("people_suggestions", ({override, mock_template}) => {
         user_id: 202,
         full_name: "Bob Térry",
         avatar_url: example_avatar_url,
+        is_guest: false,
     };
 
     const alice = {
@@ -917,6 +918,31 @@ test("people_suggestions", ({override, mock_template}) => {
     assert.equal(get_avatar_url("sender:bob@zulip.com"), expectedString);
     assert.equal(get_avatar_url("dm-including:bob@zulip.com"), expectedString);
 
+    function get_should_add_guest_user_indicator(q) {
+        return suggestions.lookup_table.get(q).user_pill_context.should_add_guest_user_indicator;
+    }
+
+    page_params.realm_enable_guest_user_indicator = true;
+    suggestions = get_suggestions(query);
+
+    assert.equal(get_should_add_guest_user_indicator("dm:bob@zulip.com"), false);
+    assert.equal(get_should_add_guest_user_indicator("sender:bob@zulip.com"), false);
+    assert.equal(get_should_add_guest_user_indicator("dm-including:bob@zulip.com"), false);
+
+    bob.is_guest = true;
+    suggestions = get_suggestions(query);
+
+    assert.equal(get_should_add_guest_user_indicator("dm:bob@zulip.com"), true);
+    assert.equal(get_should_add_guest_user_indicator("sender:bob@zulip.com"), true);
+    assert.equal(get_should_add_guest_user_indicator("dm-including:bob@zulip.com"), true);
+
+    page_params.realm_enable_guest_user_indicator = false;
+    suggestions = get_suggestions(query);
+
+    assert.equal(get_should_add_guest_user_indicator("dm:bob@zulip.com"), false);
+    assert.equal(get_should_add_guest_user_indicator("sender:bob@zulip.com"), false);
+    assert.equal(get_should_add_guest_user_indicator("dm-including:bob@zulip.com"), false);
+
     suggestions = get_suggestions("Ted "); // note space
 
     expected = ["Ted", "sender:ted@zulip.com", "dm:ted@zulip.com", "dm-including:ted@zulip.com"];
diff --git a/web/tests/settings_user_groups_legacy.test.js b/web/tests/settings_user_groups_legacy.test.js
index 8174e6d7b6..dedcce4bfd 100644
--- a/web/tests/settings_user_groups_legacy.test.js
+++ b/web/tests/settings_user_groups_legacy.test.js
@@ -306,7 +306,7 @@ test_ui("populate_user_groups", ({mock_template, override, override_rewire}) =>
             assert.ok(get_by_email_called);
             assert.equal(typeof res, "object");
             assert.equal(res.user_id, bob.user_id);
-            assert.equal(res.display_value, bob.full_name + " (deactivated)");
+            assert.equal(res.display_value, bob.full_name);
             assert.ok(res.deactivated);
             people.add_active_user(bob);
         })();
diff --git a/web/tests/user_pill.test.js b/web/tests/user_pill.test.js
index f0dfb9dc80..8d6565172e 100644
--- a/web/tests/user_pill.test.js
+++ b/web/tests/user_pill.test.js
@@ -36,6 +36,7 @@ const isaac_item = {
     deactivated: false,
     img_src: `http://zulip.zulipdev.com/avatar/${isaac.user_id}?s=50`,
     status_emoji_info: undefined,
+    should_add_guest_user_indicator: false,
 };
 
 let pill_widget = {};