diff --git a/nexus/src/app/instance.rs b/nexus/src/app/instance.rs
index 47cbb4ba35..3a89d0273c 100644
--- a/nexus/src/app/instance.rs
+++ b/nexus/src/app/instance.rs
@@ -173,12 +173,58 @@ impl super::Nexus {
         // TODO-robustness We need to figure out what to do with Destroyed
         // instances?  Presumably we need to clean them up at some point, but
         // not right away so that callers can see that they've been destroyed.
-        let (.., authz_instance) = LookupPath::new(opctx, &self.db_datastore)
-            .organization_name(organization_name)
-            .project_name(project_name)
-            .instance_name(instance_name)
-            .lookup_for(authz::Action::Delete)
+        let (.., authz_instance, db_instance) =
+            LookupPath::new(opctx, &self.db_datastore)
+                .organization_name(organization_name)
+                .project_name(project_name)
+                .instance_name(instance_name)
+                .fetch()
+                .await?;
+
+        opctx.authorize(authz::Action::Delete, &authz_instance).await?;
+
+        match db_instance.runtime_state.state.state() {
+            InstanceState::Stopped | InstanceState::Failed => {
+                // ok
+            }
+
+            state => {
+                return Err(Error::InvalidRequest {
+                    message: format!(
+                        "instance cannot be deleted in state \"{}\"",
+                        state,
+                    ),
+                });
+            }
+        }
+
+        // Detach all attached disks
+        let disks = self
+            .instance_list_disks(
+                opctx,
+                organization_name,
+                project_name,
+                instance_name,
+                &DataPageParams {
+                    marker: None,
+                    direction: dropshot::PaginationOrder::Ascending,
+                    limit: std::num::NonZeroU32::new(MAX_DISKS_PER_INSTANCE)
+                        .unwrap(),
+                },
+            )
             .await?;
+
+        for disk in &disks {
+            self.instance_detach_disk(
+                opctx,
+                organization_name,
+                project_name,
+                instance_name,
+                &disk.name(),
+            )
+            .await?;
+        }
+
         self.db_datastore.project_delete_instance(opctx, &authz_instance).await
     }
 
diff --git a/nexus/src/db/datastore.rs b/nexus/src/db/datastore.rs
index a6b2ba3e46..51b0dddacd 100644
--- a/nexus/src/db/datastore.rs
+++ b/nexus/src/db/datastore.rs
@@ -1024,6 +1024,7 @@ impl DataStore {
                     ErrorHandler::NotFoundByResource(authz_instance),
                 )
             })?;
+
         match result.status {
             UpdateStatus::Updated => Ok(()),
             UpdateStatus::NotUpdatedButExists => {
diff --git a/nexus/tests/integration_tests/instances.rs b/nexus/tests/integration_tests/instances.rs
index 3b2ead4b79..dcead06384 100644
--- a/nexus/tests/integration_tests/instances.rs
+++ b/nexus/tests/integration_tests/instances.rs
@@ -1527,6 +1527,154 @@ async fn test_cannot_attach_faulted_disks(cptestctx: &ControlPlaneTestContext) {
     }
 }
 
+// Test that disks are detached when instance is destroyed
+#[nexus_test]
+async fn test_disks_detached_when_instance_destroyed(
+    cptestctx: &ControlPlaneTestContext,
+) {
+    let client = &cptestctx.external_client;
+
+    const ORGANIZATION_NAME: &str = "bobs-barrel-of-bytes";
+    const PROJECT_NAME: &str = "bit-barrel";
+
+    // Test pre-reqs
+    DiskTest::new(&cptestctx).await;
+    create_organization(&client, ORGANIZATION_NAME).await;
+    create_project(client, ORGANIZATION_NAME, PROJECT_NAME).await;
+
+    // Make 8 disks
+    for i in 0..8 {
+        create_disk(
+            &client,
+            ORGANIZATION_NAME,
+            PROJECT_NAME,
+            &format!("probablydata{}", i,),
+        )
+        .await;
+    }
+
+    // Assert we created 8 disks
+    let url_project_disks = format!(
+        "/organizations/{}/projects/{}/disks",
+        ORGANIZATION_NAME, PROJECT_NAME,
+    );
+    let disks: Vec<Disk> = NexusRequest::iter_collection_authn(
+        client,
+        &url_project_disks,
+        "",
+        None,
+    )
+    .await
+    .expect("failed to list disks")
+    .all_items;
+
+    assert_eq!(disks.len(), 8);
+    for disk in &disks {
+        assert_eq!(disk.state, DiskState::Detached);
+    }
+
+    // Boot the instance
+    let instance_params = params::InstanceCreate {
+        identity: IdentityMetadataCreateParams {
+            name: Name::try_from(String::from("nfs")).unwrap(),
+            description: String::from("probably serving data"),
+        },
+        ncpus: InstanceCpuCount::try_from(2).unwrap(),
+        memory: ByteCount::from_mebibytes_u32(4),
+        hostname: String::from("nfs"),
+        user_data: vec![],
+        network_interfaces: params::InstanceNetworkInterfaceAttachment::Default,
+        disks: (0..8)
+            .map(|i| {
+                params::InstanceDiskAttachment::Attach(
+                    params::InstanceDiskAttach {
+                        name: Name::try_from(
+                            format!("probablydata{}", i).to_string(),
+                        )
+                        .unwrap(),
+                    },
+                )
+            })
+            .collect(),
+    };
+
+    let url_instances = format!(
+        "/organizations/{}/projects/{}/instances",
+        ORGANIZATION_NAME, PROJECT_NAME
+    );
+
+    let builder =
+        RequestBuilder::new(client, http::Method::POST, &url_instances)
+            .body(Some(&instance_params))
+            .expect_status(Some(http::StatusCode::CREATED));
+
+    let _response = NexusRequest::new(builder)
+        .authn_as(AuthnMode::PrivilegedUser)
+        .execute()
+        .await
+        .expect("expected instance creation!");
+
+    // Assert disks are attached
+    let url_project_disks = format!(
+        "/organizations/{}/projects/{}/disks",
+        ORGANIZATION_NAME, PROJECT_NAME,
+    );
+    let disks: Vec<Disk> = NexusRequest::iter_collection_authn(
+        client,
+        &url_project_disks,
+        "",
+        None,
+    )
+    .await
+    .expect("failed to list disks")
+    .all_items;
+
+    assert_eq!(disks.len(), 8);
+    for disk in &disks {
+        assert!(matches!(disk.state, DiskState::Attached(_)));
+    }
+
+    // Stop and delete instance
+    let instance_url = format!(
+        "/organizations/{}/projects/{}/instances/nfs",
+        ORGANIZATION_NAME, PROJECT_NAME
+    );
+
+    let instance =
+        instance_post(&client, &instance_url, InstanceOp::Stop).await;
+    let apictx = &cptestctx.server.apictx;
+    let nexus = &apictx.nexus;
+    instance_simulate(nexus, &instance.identity.id).await;
+    let instance = instance_get(&client, &instance_url).await;
+    assert_eq!(instance.runtime.run_state, InstanceState::Stopped);
+
+    NexusRequest::object_delete(&client, &instance_url)
+        .authn_as(AuthnMode::PrivilegedUser)
+        .execute()
+        .await
+        .unwrap();
+
+    // Assert disks are detached
+    let url_project_disks = format!(
+        "/organizations/{}/projects/{}/disks",
+        ORGANIZATION_NAME, PROJECT_NAME,
+    );
+    let disks: Vec<Disk> = NexusRequest::iter_collection_authn(
+        client,
+        &url_project_disks,
+        "",
+        None,
+    )
+    .await
+    .expect("failed to list disks")
+    .all_items;
+
+    assert_eq!(disks.len(), 8);
+    for disk in &disks {
+        assert_eq!(disk.state, DiskState::Detached);
+    }
+}
+
 async fn instance_get(
     client: &ClientTestContext,
     instance_url: &str,