diff --git a/src/matrix/room/timeline/entries/BaseEventEntry.js b/src/matrix/room/timeline/entries/BaseEventEntry.js
index ec20f48a..dbcfce94 100644
--- a/src/matrix/room/timeline/entries/BaseEventEntry.js
+++ b/src/matrix/room/timeline/entries/BaseEventEntry.js
@@ -16,9 +16,9 @@ limitations under the License.
 
 import {BaseEntry} from "./BaseEntry";
 import {REDACTION_TYPE} from "../../common.js";
-import {createAnnotation, ANNOTATION_RELATION_TYPE, getRelationFromContent} from "../relations.js";
+import {createAnnotation, ANNOTATION_RELATION_TYPE, THREADING_RELATION_TYPE, getRelationFromContent} from "../relations.js";
 import {PendingAnnotation} from "../PendingAnnotation.js";
-import {createReplyContent} from "./reply.js"
+import {createReplyContent} from "./reply.js";
 
 /** Deals mainly with local echo for relations and redactions,
  * so it is shared between PendingEventEntry and EventEntry */
@@ -32,7 +32,11 @@ export class BaseEventEntry extends BaseEntry {
     }
 
     get isReply() {
-        return !!this.relation?.["m.in_reply_to"];
+        return !!this.relation?.["m.in_reply_to"] || this.isThread;
+    }
+
+    get isThread() {
+        return this.relation?.["rel_type"] === THREADING_RELATION_TYPE;
     }
 
     get isRedacting() {
diff --git a/src/matrix/room/timeline/entries/EventEntry.js b/src/matrix/room/timeline/entries/EventEntry.js
index 7b957e01..3d9c982b 100644
--- a/src/matrix/room/timeline/entries/EventEntry.js
+++ b/src/matrix/room/timeline/entries/EventEntry.js
@@ -124,6 +124,13 @@ export class EventEntry extends BaseEventEntry {
         return getRelatedEventId(this.event);
     }
 
+    get threadEventId() {
+        if (this.isThread) {
+            return this.relation?.event_id;
+        }
+        return null;
+    }
+
     get isRedacted() {
         return super.isRedacted || isRedacted(this._eventEntry.event);
     }
diff --git a/src/matrix/room/timeline/entries/reply.js b/src/matrix/room/timeline/entries/reply.js
index 2e180c11..fcc6f56f 100644
--- a/src/matrix/room/timeline/entries/reply.js
+++ b/src/matrix/room/timeline/entries/reply.js
@@ -14,6 +14,8 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
+import {THREADING_RELATION_TYPE} from "../relations.js";
+
 function htmlEscape(string) {
     return string.replace(/&/g, "&amp;").replace(/</g, "&lt;").replace(/>/g, "&gt;");
 }
@@ -36,8 +38,8 @@ function fallbackPrefix(msgtype) {
     return msgtype === "m.emote" ? "* " : "";
 }
 
-function _createReplyContent(targetId, msgtype, body, formattedBody) {
-    return {
+function _createReplyContent(targetId, msgtype, body, formattedBody, threadId) {
+    const reply =  {
         msgtype,
         body,
         "format": "org.matrix.custom.html",
@@ -48,10 +50,16 @@ function _createReplyContent(targetId, msgtype, body, formattedBody) {
             }
         }
     };
+    if (threadId) {
+        Object.assign(reply["m.relates_to"], {
+            rel_type: THREADING_RELATION_TYPE,
+            event_id: threadId,
+        });
+    }
+    return reply;
 }
 
 export function createReplyContent(entry, msgtype, body) {
-    // TODO check for absense of sender / body / msgtype / etc?
     const nonTextual = fallbackForNonTextualMessage(entry.content.msgtype);
     const prefix = fallbackPrefix(entry.content.msgtype);
     const sender = entry.sender;
@@ -70,5 +78,5 @@ export function createReplyContent(entry, msgtype, body) {
 
     const newBody = plainFallback + '\n\n' + body;
     const newFormattedBody = formattedFallback + htmlEscape(body);
-    return _createReplyContent(entry.id, msgtype, newBody, newFormattedBody);
+    return _createReplyContent(entry.id, msgtype, newBody, newFormattedBody, entry.threadEventId);
 }
diff --git a/src/matrix/room/timeline/relations.js b/src/matrix/room/timeline/relations.js
index 4009d8c4..d92847ec 100644
--- a/src/matrix/room/timeline/relations.js
+++ b/src/matrix/room/timeline/relations.js
@@ -18,6 +18,7 @@ import {REDACTION_TYPE} from "../common.js";
 
 export const REACTION_TYPE = "m.reaction";
 export const ANNOTATION_RELATION_TYPE = "m.annotation";
+export const THREADING_RELATION_TYPE = "io.element.thread";
 
 export function createAnnotation(targetId, key) {
     return {
@@ -30,7 +31,7 @@ export function createAnnotation(targetId, key) {
 }
 
 export function getRelationTarget(relation) {
-    return relation.event_id || relation["m.in_reply_to"]?.event_id
+    return relation["m.in_reply_to"]?.event_id || relation.event_id;
 }
 
 export function setRelationTarget(relation, target) {