diff --git a/ruma-events/src/lib.rs b/ruma-events/src/lib.rs
index 3f450f06..b90ab8c6 100644
--- a/ruma-events/src/lib.rs
+++ b/ruma-events/src/lib.rs
@@ -238,6 +238,8 @@ pub mod push_rules;
 #[cfg(feature = "unstable-pre-spec")]
 pub mod reaction;
 pub mod receipt;
+#[cfg(feature = "unstable-pre-spec")]
+pub mod relation;
 pub mod room;
 pub mod room_key;
 pub mod room_key_request;
@@ -245,6 +247,8 @@ pub mod sticker;
 pub mod tag;
 pub mod typing;
 
+#[cfg(feature = "unstable-pre-spec")]
+pub use self::relation::Relations;
 pub use self::{
     enums::{
         AnyBasicEvent, AnyBasicEventContent, AnyEphemeralRoomEvent, AnyEphemeralRoomEventContent,
@@ -282,6 +286,11 @@ pub struct Unsigned {
     /// is the same one which sent it.
     #[serde(skip_serializing_if = "Option::is_none")]
     pub transaction_id: Option<String>,
+
+    /// Server-compiled information from other events relating to this event.
+    #[cfg(feature = "unstable-pre-spec")]
+    #[serde(rename = "m.relations", skip_serializing_if = "Option::is_none")]
+    pub relations: Option<Relations>,
 }
 
 impl Unsigned {
diff --git a/ruma-events/src/policy/rule/room.rs b/ruma-events/src/policy/rule/room.rs
index cc766314..4ec2699d 100644
--- a/ruma-events/src/policy/rule/room.rs
+++ b/ruma-events/src/policy/rule/room.rs
@@ -36,7 +36,12 @@ mod tests {
             room_id: room_id!("!jEsUZKDJdhlrceRyVU:example.org"),
             state_key: "rule:#*:example.org".into(),
             prev_content: None,
-            unsigned: Unsigned { age: Some(1234.into()), transaction_id: None },
+            unsigned: Unsigned {
+                age: Some(1234.into()),
+                transaction_id: None,
+                #[cfg(feature = "unstable-pre-spec")]
+                relations: None,
+            },
             content: RoomEventContent(PolicyRuleEventContent {
                 entity: "#*:example.org".into(),
                 reason: "undesirable content".into(),
diff --git a/ruma-events/src/relation.rs b/ruma-events/src/relation.rs
new file mode 100644
index 00000000..f405da56
--- /dev/null
+++ b/ruma-events/src/relation.rs
@@ -0,0 +1,77 @@
+//! Types describing event relations after MSC 2674, 2675, 2676, 2677.
+
+use std::{fmt::Debug, time::SystemTime};
+
+use js_int::UInt;
+use serde::{Deserialize, Serialize};
+
+/// Summary of all reactions with the given key to an event.
+#[derive(Clone, Debug, Default, Deserialize, PartialEq, Eq, Serialize)]
+#[cfg_attr(not(feature = "unstable-exhaustive-types"), non_exhaustive)]
+pub struct BundledReaction {
+    /// The key (emoji) used for reaction.
+    pub key: String,
+
+    /// Time of the bundled reaction being compiled on the server.
+    #[serde(
+        with = "ruma_serde::time::opt_ms_since_unix_epoch",
+        default,
+        skip_serializing_if = "Option::is_none"
+    )]
+    pub origin_server_ts: Option<SystemTime>,
+
+    /// Number of reactions.
+    pub count: UInt,
+}
+
+impl BundledReaction {
+    /// Creates a new `BundledReaction`.
+    pub fn new(key: String, origin_server_ts: Option<SystemTime>, count: UInt) -> Self {
+        Self { key, origin_server_ts, count }
+    }
+}
+
+/// Type of bundled annotation.
+#[derive(Clone, Debug, Deserialize, Serialize)]
+#[cfg_attr(not(feature = "unstable-exhaustive-types"), non_exhaustive)]
+#[serde(tag = "type")]
+pub enum BundledAnnotation {
+    /// An emoji reaction and its count.
+    #[serde(rename = "m.reaction")]
+    Reaction(BundledReaction),
+}
+
+/// The first chunk of annotations with a token for loading more.
+#[derive(Clone, Debug, Default, Deserialize, Serialize)]
+#[cfg_attr(not(feature = "unstable-exhaustive-types"), non_exhaustive)]
+pub struct AnnotationChunk {
+    /// The first batch of bundled annotations.
+    pub chunk: Vec<BundledAnnotation>,
+
+    /// Token to receive the next annotation batch.
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub next_batch: Option<String>,
+}
+
+impl AnnotationChunk {
+    /// Creates a new `AnnotationChunk`.
+    pub fn new(chunk: Vec<BundledAnnotation>, next_batch: Option<String>) -> Self {
+        Self { chunk, next_batch }
+    }
+}
+
+/// Precompiled list of relations to this event grouped by relation type.
+#[derive(Clone, Debug, Default, Deserialize, Serialize)]
+#[cfg_attr(not(feature = "unstable-exhaustive-types"), non_exhaustive)]
+pub struct Relations {
+    /// Annotation relations.
+    #[serde(rename = "m.annotation")]
+    pub annotation: Option<AnnotationChunk>,
+}
+
+impl Relations {
+    /// Creates a new `Relations` struct.
+    pub fn new(annotation: Option<AnnotationChunk>) -> Self {
+        Self { annotation }
+    }
+}