diff --git a/src/main/scala/gitbucket/core/api/CreateAMilestone.scala b/src/main/scala/gitbucket/core/api/CreateAMilestone.scala
new file mode 100644
index 0000000..39cdc60
--- /dev/null
+++ b/src/main/scala/gitbucket/core/api/CreateAMilestone.scala
@@ -0,0 +1,14 @@
+package gitbucket.core.api
+
+import java.util.Date
+
+case class CreateAMilestone(
+  title: String,
+  state: String = "open",
+  description: Option[String],
+  due_on: Option[Date]
+) {
+  def isValid: Boolean = {
+    title.length <= 100 && title.matches("[a-zA-Z0-9\\-\\+_.]+")
+  }
+}
diff --git a/src/main/scala/gitbucket/core/controller/api/ApiIssueMilestoneControllerBase.scala b/src/main/scala/gitbucket/core/controller/api/ApiIssueMilestoneControllerBase.scala
index 5b38a58..7de096b 100644
--- a/src/main/scala/gitbucket/core/controller/api/ApiIssueMilestoneControllerBase.scala
+++ b/src/main/scala/gitbucket/core/controller/api/ApiIssueMilestoneControllerBase.scala
@@ -1,7 +1,9 @@
 package gitbucket.core.controller.api
 import gitbucket.core.api._
 import gitbucket.core.controller.ControllerBase
+import gitbucket.core.model.Repository
 import gitbucket.core.service.MilestonesService
+import gitbucket.core.service.RepositoryService.RepositoryInfo
 import gitbucket.core.util.{ReferrerAuthenticator, WritableUsersAuthenticator}
 import gitbucket.core.util.Implicits._
 import org.scalatra.NoContent
@@ -41,6 +43,21 @@
    * ii. Create a milestone
    * https://docs.github.com/en/rest/reference/issues#create-a-milestone
    */
+  post("/api/v3/repos/:owner/:repository/milestones")(writableUsersOnly { repository =>
+    (for {
+      data <- extractFromJsonBody[CreateAMilestone] if data.isValid
+      milestoneId = createMilestone(
+        repository.owner,
+        repository.name,
+        data.title,
+        data.description,
+        data.due_on
+      )
+      apiMilestone <- getApiMilestone(repository, milestoneId)
+    } yield {
+      JsonFormat(apiMilestone)
+    }) getOrElse NotFound()
+  })
 
   /*
    * iii. Get a milestone
@@ -48,26 +65,34 @@
    */
   get("/api/v3/repos/:owner/:repository/milestones/:number")(referrersOnly { repository =>
     val milestoneId = params("number").toInt // use milestoneId as number
-    getMilestonesWithIssueCount(repository.owner, repository.name)
-      .find(p => p._1.milestoneId == milestoneId) match {
-      case Some(milestoneWithIssue) =>
-        JsonFormat(
-          ApiMilestone(
-            repository.repository,
-            milestoneWithIssue._1,
-            ApiUser(context.loginAccount.get),
-            milestoneWithIssue._2,
-            milestoneWithIssue._3
-          )
-        )
-      case _ => NotFound()
-    }
+    (for (apiMilestone <- getApiMilestone(repository, milestoneId)) yield {
+      JsonFormat(apiMilestone)
+    }) getOrElse NotFound()
   })
 
   /*
    * iv.Update a milestone
    * https://docs.github.com/en/rest/reference/issues#update-a-milestone
    */
+  patch("/api/v3/repos/:owner/:repository/milestones/:number")(writableUsersOnly { repository =>
+    val milestoneId = params("number").toInt
+    (for {
+      data <- extractFromJsonBody[CreateAMilestone] if data.isValid
+      milestone <- getMilestone(repository.owner, repository.name, milestoneId)
+      _ = (data.state, milestone.closedDate) match {
+        case ("open", Some(_)) =>
+          openMilestone(milestone)
+        case ("closed", None) =>
+          closeMilestone(milestone)
+        case _ =>
+      }
+      milestone <- getMilestone(repository.owner, repository.name, milestoneId)
+      _ = updateMilestone(milestone.copy(title = data.title, description = data.description, dueDate = data.due_on))
+      apiMilestone <- getApiMilestone(repository, milestoneId)
+    } yield {
+      JsonFormat(apiMilestone)
+    }) getOrElse NotFound()
+  })
 
   /*
    * v. Delete a milestone
@@ -78,4 +103,19 @@
     deleteMilestone(repository.owner, repository.name, milestoneId)
     NoContent()
   })
+
+  private def getApiMilestone(repository: RepositoryInfo, milestoneId: Int): Option[ApiMilestone] = {
+    getMilestonesWithIssueCount(repository.owner, repository.name)
+      .find(p => p._1.milestoneId == milestoneId)
+      .map(
+        milestoneWithIssue =>
+          ApiMilestone(
+            repository.repository,
+            milestoneWithIssue._1,
+            ApiUser(context.loginAccount.get),
+            milestoneWithIssue._2,
+            milestoneWithIssue._3
+        )
+      )
+  }
 }
diff --git a/src/main/scala/gitbucket/core/service/MilestonesService.scala b/src/main/scala/gitbucket/core/service/MilestonesService.scala
index ae1ce1e..f5f9849 100644
--- a/src/main/scala/gitbucket/core/service/MilestonesService.scala
+++ b/src/main/scala/gitbucket/core/service/MilestonesService.scala
@@ -13,8 +13,8 @@
     title: String,
     description: Option[String],
     dueDate: Option[java.util.Date]
-  )(implicit s: Session): Unit =
-    Milestones insert Milestone(
+  )(implicit s: Session): Int = {
+    Milestones returning Milestones.map(_.milestoneId) insert Milestone(
       userName = owner,
       repositoryName = repository,
       title = title,
@@ -22,6 +22,7 @@
       dueDate = dueDate,
       closedDate = None
     )
+  }
 
   def updateMilestone(milestone: Milestone)(implicit s: Session): Unit =
     Milestones