diff --git a/domain/src/main/kotlin/com/threedays/domain/chat/entity/ChatMember.kt b/domain/src/main/kotlin/com/threedays/domain/chat/entity/ChatMember.kt
new file mode 100644
index 0000000..74cebd5
--- /dev/null
+++ b/domain/src/main/kotlin/com/threedays/domain/chat/entity/ChatMember.kt
@@ -0,0 +1,17 @@
+package com.threedays.domain.chat.entity
+
+import com.threedays.domain.user.entity.User
+import com.threedays.support.common.base.domain.DomainEntity
+import com.threedays.support.common.base.domain.TypeId
+import java.time.LocalDateTime
+import java.util.*
+
+data class ChatMember(
+    override val id: Id,
+    val userId: User.Id,
+    val joinedAt: LocalDateTime = LocalDateTime.now()
+) : DomainEntity<ChatMember, ChatMember.Id>() {
+
+    data class Id(override val value: UUID) : TypeId<UUID>(value)
+
+}
diff --git a/domain/src/main/kotlin/com/threedays/domain/chat/entity/ChatMessage.kt b/domain/src/main/kotlin/com/threedays/domain/chat/entity/ChatMessage.kt
new file mode 100644
index 0000000..9637ce1
--- /dev/null
+++ b/domain/src/main/kotlin/com/threedays/domain/chat/entity/ChatMessage.kt
@@ -0,0 +1,53 @@
+package com.threedays.domain.chat.entity
+
+import com.threedays.support.common.base.domain.AggregateRoot
+import com.threedays.support.common.base.domain.TypeId
+import java.time.LocalDateTime
+import java.util.*
+
+data class ChatMessage(
+    override val id: Id,
+    val chatRoomId: ChatRoom.Id,
+    val senderId: ChatMember.Id,
+    val content: String,
+    val status: Status = Status.SENT,
+    val createdAt: LocalDateTime = LocalDateTime.now(),
+    val updatedAt: LocalDateTime? = null,
+    val failureReason: FailureReason? = null
+) : AggregateRoot<ChatMessage, ChatMessage.Id>() {
+
+    data class Id(override val value: UUID) : TypeId<UUID>(value)
+
+
+    enum class Status {
+        SENT,
+        READ,
+        FAILED,
+    }
+
+    enum class FailureReason {
+        NETWORK_ERROR,
+        INVALID_RECIPIENT,
+        MESSAGE_TOO_LARGE,
+        UNKNOWN_ERROR
+    }
+
+    fun markAsRead(): ChatMessage {
+        require(status == Status.SENT) { "메시지가 전송된 상태에서만 읽음 처리가 가능합니다" }
+        return this.copy(
+            status = Status.READ,
+            updatedAt = LocalDateTime.now()
+        )
+    }
+
+
+    fun markAsFailed(reason: FailureReason) {
+        require(status == Status.SENT) { "전송된 상태의 메시지만 실패 처리가 가능합니다" }
+        this.copy(
+            status = Status.FAILED,
+            updatedAt = LocalDateTime.now(),
+            failureReason = reason
+        )
+    }
+
+}
diff --git a/domain/src/main/kotlin/com/threedays/domain/chat/entity/ChatRoom.kt b/domain/src/main/kotlin/com/threedays/domain/chat/entity/ChatRoom.kt
new file mode 100644
index 0000000..fa9ffbe
--- /dev/null
+++ b/domain/src/main/kotlin/com/threedays/domain/chat/entity/ChatRoom.kt
@@ -0,0 +1,19 @@
+package com.threedays.domain.chat.entity
+
+import com.threedays.domain.connection.entity.Connection
+import com.threedays.support.common.base.domain.AggregateRoot
+import com.threedays.support.common.base.domain.TypeId
+import java.time.LocalDateTime
+import java.util.UUID
+
+data class ChatRoom(
+    override val id: Id,
+    val connectionId: Connection.Id,
+    val members: List<ChatMember>,
+    val createdAt: LocalDateTime = LocalDateTime.now()
+) : AggregateRoot<ChatRoom, ChatRoom.Id>() {
+
+    data class Id(override val value: UUID) : TypeId<UUID>(value)
+
+
+}
diff --git a/domain/src/main/kotlin/com/threedays/domain/connection/entity/Connection.kt b/domain/src/main/kotlin/com/threedays/domain/connection/entity/Connection.kt
new file mode 100644
index 0000000..f66bead
--- /dev/null
+++ b/domain/src/main/kotlin/com/threedays/domain/connection/entity/Connection.kt
@@ -0,0 +1,13 @@
+package com.threedays.domain.connection.entity
+
+import com.threedays.support.common.base.domain.AggregateRoot
+import com.threedays.support.common.base.domain.UUIDTypeId
+import java.util.UUID
+
+data class Connection(
+    override val id: Id,
+): AggregateRoot<Connection, Connection.Id>() {
+
+    data class Id(override val value: UUID) : UUIDTypeId(value)
+
+}
diff --git a/openapi b/openapi
index b0457c3..b4118d6 160000
--- a/openapi
+++ b/openapi
@@ -1 +1 @@
-Subproject commit b0457c3105b260405e5bb3eb07ad9943525acf34
+Subproject commit b4118d6a2e2cf6d57430fe47d6c4a45b9f9817e8