diff --git a/cli/tests/unit/os_test.ts b/cli/tests/unit/os_test.ts
index 5e88f02c19..ae2bee72e3 100644
--- a/cli/tests/unit/os_test.ts
+++ b/cli/tests/unit/os_test.ts
@@ -239,6 +239,18 @@ Deno.test({ permissions: { sys: false } }, function releasePerm() {
   }, Deno.errors.PermissionDenied);
 });
 
+Deno.test({ permissions: { sys: ["osUptime"] } }, function osUptime() {
+  const uptime = Deno.osUptime();
+  assert(typeof uptime === "number");
+  assert(uptime > 0);
+});
+
+Deno.test({ permissions: { sys: false } }, function osUptimePerm() {
+  assertThrows(() => {
+    Deno.osUptime();
+  }, Deno.errors.PermissionDenied);
+});
+
 Deno.test(
   { permissions: { sys: ["systemMemoryInfo"] } },
   function systemMemoryInfo() {
diff --git a/cli/tests/unit/permissions_test.ts b/cli/tests/unit/permissions_test.ts
index 3387913e87..3af2e35eaa 100644
--- a/cli/tests/unit/permissions_test.ts
+++ b/cli/tests/unit/permissions_test.ts
@@ -22,6 +22,7 @@ Deno.test(async function permissionNetInvalidHost() {
 Deno.test(async function permissionSysValidKind() {
   await Deno.permissions.query({ name: "sys", kind: "loadavg" });
   await Deno.permissions.query({ name: "sys", kind: "osRelease" });
+  await Deno.permissions.query({ name: "sys", kind: "osUptime" });
   await Deno.permissions.query({ name: "sys", kind: "networkInterfaces" });
   await Deno.permissions.query({ name: "sys", kind: "systemMemoryInfo" });
   await Deno.permissions.query({ name: "sys", kind: "hostname" });
diff --git a/cli/tsc/diagnostics.rs b/cli/tsc/diagnostics.rs
index 4413398c24..8323fd7ac4 100644
--- a/cli/tsc/diagnostics.rs
+++ b/cli/tsc/diagnostics.rs
@@ -46,6 +46,7 @@ const UNSTABLE_DENO_PROPS: &[&str] = &[
   "ServeInit",
   "ServeTlsInit",
   "Handler",
+  "osUptime",
 ];
 
 static MSG_MISSING_PROPERTY_DENO: Lazy<Regex> = Lazy::new(|| {
diff --git a/cli/tsc/dts/lib.deno.ns.d.ts b/cli/tsc/dts/lib.deno.ns.d.ts
index fa68dc1bdd..4dafd73888 100644
--- a/cli/tsc/dts/lib.deno.ns.d.ts
+++ b/cli/tsc/dts/lib.deno.ns.d.ts
@@ -4120,6 +4120,7 @@ declare namespace Deno {
       | "systemMemoryInfo"
       | "networkInterfaces"
       | "osRelease"
+      | "osUptime"
       | "uid"
       | "gid";
   }
diff --git a/cli/tsc/dts/lib.deno.unstable.d.ts b/cli/tsc/dts/lib.deno.unstable.d.ts
index f1b8d99e90..77d3505037 100644
--- a/cli/tsc/dts/lib.deno.unstable.d.ts
+++ b/cli/tsc/dts/lib.deno.unstable.d.ts
@@ -1691,6 +1691,21 @@ declare namespace Deno {
     /** The buffered output from the child process' `stderr`. */
     readonly stderr: Uint8Array;
   }
+
+  /** **UNSTABLE**: New API, yet to be vetted.
+   *
+   * Returns the Operating System uptime in number of seconds.
+   *
+   * ```ts
+   * console.log(Deno.osUptime());
+   * ```
+   *
+   * Requires `allow-sys` permission.
+   *
+   * @tags allow-sys
+   * @category Runtime Environment
+   */
+  export function osUptime(): number;
 }
 
 /** **UNSTABLE**: New API, yet to be vetted.
diff --git a/runtime/js/30_os.js b/runtime/js/30_os.js
index 723b521329..3c9768593b 100644
--- a/runtime/js/30_os.js
+++ b/runtime/js/30_os.js
@@ -25,6 +25,10 @@
     return ops.op_os_release();
   }
 
+  function osUptime() {
+    return ops.op_os_uptime();
+  }
+
   function systemMemoryInfo() {
     return ops.op_system_memory_info();
   }
@@ -106,6 +110,7 @@
     loadavg,
     networkInterfaces,
     osRelease,
+    osUptime,
     setExitHandler,
     systemMemoryInfo,
     uid,
diff --git a/runtime/js/90_deno_ns.js b/runtime/js/90_deno_ns.js
index 94a6114564..f49fb5af14 100644
--- a/runtime/js/90_deno_ns.js
+++ b/runtime/js/90_deno_ns.js
@@ -119,6 +119,7 @@
     refTimer: __bootstrap.timers.refTimer,
     unrefTimer: __bootstrap.timers.unrefTimer,
     osRelease: __bootstrap.os.osRelease,
+    osUptime: __bootstrap.os.osUptime,
     hostname: __bootstrap.os.hostname,
     systemMemoryInfo: __bootstrap.os.systemMemoryInfo,
     networkInterfaces: __bootstrap.os.networkInterfaces,
diff --git a/runtime/ops/os/mod.rs b/runtime/ops/os/mod.rs
index 613b4507db..e82afbf7cd 100644
--- a/runtime/ops/os/mod.rs
+++ b/runtime/ops/os/mod.rs
@@ -29,6 +29,7 @@ fn init_ops(builder: &mut ExtensionBuilder) -> &mut ExtensionBuilder {
     op_loadavg::decl(),
     op_network_interfaces::decl(),
     op_os_release::decl(),
+    op_os_uptime::decl(),
     op_set_env::decl(),
     op_set_exit_code::decl(),
     op_system_memory_info::decl(),
@@ -423,3 +424,13 @@ fn rss() -> usize {
     }
   }
 }
+
+#[op]
+fn op_os_uptime(state: &mut OpState) -> Result<u64, AnyError> {
+  super::check_unstable(state, "Deno.osUptime");
+  state
+    .borrow_mut::<Permissions>()
+    .sys
+    .check("osUptime", Some("Deno.osUptime()"))?;
+  Ok(sys_info::os_uptime())
+}
diff --git a/runtime/ops/os/sys_info.rs b/runtime/ops/os/sys_info.rs
index 40de7cc4b0..ecb40b9a04 100644
--- a/runtime/ops/os/sys_info.rs
+++ b/runtime/ops/os/sys_info.rs
@@ -300,3 +300,65 @@ pub fn mem_info() -> Option<MemInfo> {
 
   Some(mem_info)
 }
+
+pub fn os_uptime() -> u64 {
+  #[cfg(target_os = "linux")]
+  {
+    let mut info = std::mem::MaybeUninit::uninit();
+    // SAFETY: `info` is a valid pointer to a `libc::sysinfo` struct.
+    let res = unsafe { libc::sysinfo(info.as_mut_ptr()) };
+    if res == 0 {
+      // SAFETY: `sysinfo` initializes the struct.
+      let info = unsafe { info.assume_init() };
+      return info.uptime as u64;
+    }
+  }
+
+  #[cfg(any(
+    target_vendor = "apple",
+    target_os = "freebsd",
+    target_os = "openbsd"
+  ))]
+  {
+    use std::mem;
+    use std::time::Duration;
+    use std::time::SystemTime;
+    let mut request = [libc::CTL_KERN, libc::KERN_BOOTTIME];
+    // SAFETY: `boottime` is only accessed if sysctl() succeeds
+    // and agrees with the `size` set by sysctl().
+    let mut boottime: libc::timeval = unsafe { mem::zeroed() };
+    let mut size: libc::size_t = mem::size_of_val(&boottime) as libc::size_t;
+    // SAFETY: `sysctl` is thread-safe.
+    let res = unsafe {
+      libc::sysctl(
+        &mut request[0],
+        2,
+        &mut boottime as *mut libc::timeval as *mut libc::c_void,
+        &mut size,
+        std::ptr::null_mut(),
+        0,
+      )
+    };
+    if res == 0 {
+      return SystemTime::now()
+        .duration_since(SystemTime::UNIX_EPOCH)
+        .map(|d| {
+          (d - Duration::new(
+            boottime.tv_sec as u64,
+            boottime.tv_usec as u32 * 1000,
+          ))
+          .as_secs()
+        })
+        .unwrap_or_default();
+    }
+  }
+
+  #[cfg(target_family = "windows")]
+  unsafe {
+    // Windows is the only one that returns `uptime` in milisecond precision,
+    // so we need to get the seconds out of it to be in sync with other envs.
+    return unsafe { winapi::um::sysinfoapi::GetTickCount64() as u64 / 1000 };
+  }
+
+  0
+}
diff --git a/runtime/permissions/mod.rs b/runtime/permissions/mod.rs
index 5b2af0e0f9..ce4984ee11 100644
--- a/runtime/permissions/mod.rs
+++ b/runtime/permissions/mod.rs
@@ -309,7 +309,7 @@ pub struct SysDescriptor(pub String);
 
 pub fn parse_sys_kind(kind: &str) -> Result<&str, AnyError> {
   match kind {
-    "hostname" | "osRelease" | "loadavg" | "networkInterfaces"
+    "hostname" | "osRelease" | "osUptime" | "loadavg" | "networkInterfaces"
     | "systemMemoryInfo" | "uid" | "gid" => Ok(kind),
     _ => Err(type_error(format!("unknown system info kind \"{}\"", kind))),
   }