diff --git a/src/cargo/ops/cargo_compile/mod.rs b/src/cargo/ops/cargo_compile/mod.rs
index 64e81fdf3a4..0a07eacd9f5 100644
--- a/src/cargo/ops/cargo_compile/mod.rs
+++ b/src/cargo/ops/cargo_compile/mod.rs
@@ -58,6 +58,8 @@ use crate::util::BuildLogger;
 use crate::util::context::{GlobalContext, WarningHandling};
 use crate::util::interning::InternedString;
 use crate::util::log_message::LogMessage;
+use crate::util::machine_message;
+use crate::util::machine_message::Message as _;
 use crate::util::{CargoResult, StableHasher};
 
 mod compile_filter;
@@ -181,6 +183,12 @@ pub fn compile_ws<'a>(
             target_dir: ws.target_dir().as_path_unlocked().to_path_buf(),
             workspace_root: ws.root().to_path_buf(),
         });
+
+        if options.build_config.emit_json() {
+            let run_id = logger.run_id().to_string();
+            let msg = machine_message::BuildStarted { run_id: &run_id }.to_json_string();
+            writeln!(ws.gctx().shell().out(), "{msg}")?;
+        }
     }
 
     let bcx = create_bcx(ws, options, &interner, logger.as_ref())?;
diff --git a/src/cargo/util/machine_message.rs b/src/cargo/util/machine_message.rs
index 6623521766c..bdc1cfd3690 100644
--- a/src/cargo/util/machine_message.rs
+++ b/src/cargo/util/machine_message.rs
@@ -103,3 +103,14 @@ impl Message for BuildFinished {
         "build-finished"
     }
 }
+
+#[derive(Serialize)]
+pub struct BuildStarted<'a> {
+    pub run_id: &'a str,
+}
+
+impl Message for BuildStarted<'_> {
+    fn reason(&self) -> &str {
+        "build-started"
+    }
+}
diff --git a/tests/testsuite/build_analysis.rs b/tests/testsuite/build_analysis.rs
index 458461bf726..4ec5d87aa65 100644
--- a/tests/testsuite/build_analysis.rs
+++ b/tests/testsuite/build_analysis.rs
@@ -719,6 +719,39 @@ fn log_msg_resolution_events() {
     );
 }
 
+#[cargo_test]
+fn json_message_build_started_with_run_id() {
+    let p = project()
+        .file("Cargo.toml", &basic_manifest("foo", "0.0.0"))
+        .file("src/lib.rs", "")
+        .build();
+
+    p.cargo("check -Zbuild-analysis --message-format=json")
+        .env("CARGO_BUILD_ANALYSIS_ENABLED", "true")
+        .masquerade_as_nightly_cargo(&["build-analysis"])
+        .with_stdout_data(
+            str![[r#"
+[
+  {
+    "reason": "build-started",
+    "run_id": "[..]T[..]Z-[..]"
+  },
+  {
+    "reason": "compiler-artifact",
+    "...": "{...}"
+  },
+  {
+    "reason": "build-finished",
+    "success": true
+  }
+]
+"#]]
+            .is_json()
+            .against_jsonlines(),
+        )
+        .run();
+}
+
 fn get_log(idx: usize) -> String {
     std::fs::read_to_string(log_file(idx)).unwrap()
 }