diff --git a/Cargo.toml b/Cargo.toml
index 9aed713be453a..b54f9065be0e5 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -56,6 +56,7 @@ targets = [
     "i686-pc-windows-msvc",
     "i686-unknown-freebsd",
     "i686-unknown-haiku",
+    "i686-unknown-helenos",
     "i686-unknown-linux-gnu",
     "i686-unknown-linux-musl",
     "i686-unknown-netbsd",
@@ -117,6 +118,7 @@ targets = [
     "x86_64-unknown-freebsd",
     "x86_64-unknown-fuchsia",
     "x86_64-unknown-haiku",
+    "x86_64-unknown-helenos",
     "x86_64-unknown-hermit",
     "x86_64-unknown-illumos",
     "x86_64-unknown-l4re-uclibc",
diff --git a/build.rs b/build.rs
index 968a85d45d5b4..30f34434cd882 100644
--- a/build.rs
+++ b/build.rs
@@ -26,7 +26,7 @@ const CHECK_CFG_EXTRA: &'static [(&'static str, &'static [&'static str])] = &[
     (
         "target_os",
         &[
-            "switch", "aix", "ohos", "hurd", "rtems", "visionos", "nuttx", "cygwin",
+            "switch", "aix", "ohos", "hurd", "rtems", "visionos", "nuttx", "cygwin", "helenos",
         ],
     ),
     ("target_env", &["illumos", "wasi", "aix", "ohos"]),
diff --git a/ci/verify-build.sh b/ci/verify-build.sh
index 8e1d7d964d251..1464ae239a24e 100755
--- a/ci/verify-build.sh
+++ b/ci/verify-build.sh
@@ -191,6 +191,7 @@ armv7r-none-eabi \
 armv7r-none-eabihf \
 i686-pc-windows-msvc \
 i686-unknown-haiku \
+i686-unknown-helenos \
 i686-unknown-netbsd \
 i686-unknown-openbsd \
 i686-wrs-vxworks \
@@ -234,6 +235,7 @@ thumbv8m.main-none-eabi \
 x86_64-pc-windows-msvc \
 x86_64-unknown-dragonfly \
 x86_64-unknown-haiku \
+x86_64-unknown-helenos \
 x86_64-unknown-hermit \
 x86_64-unknown-l4re-uclibc \
 x86_64-unknown-openbsd \
diff --git a/src/helenos.rs b/src/helenos.rs
new file mode 100644
index 0000000000000..c8a69fe880cf3
--- /dev/null
+++ b/src/helenos.rs
@@ -0,0 +1,417 @@
+use crate::prelude::*;
+
+pub type intmax_t = i64;
+pub type uintmax_t = u64;
+pub type intptr_t = isize;
+pub type uintptr_t = usize;
+pub type size_t = usize;
+pub type ssize_t = isize;
+
+// abi/include/_bits/errno.h
+pub type errno_t = c_int;
+
+// abi/include/_bits/native.h
+pub type sysarg_t = uintptr_t;
+
+// uspace/lib/c/include/fibril.h
+pub type fid_t = *mut fibril_t;
+
+// uspace/lib/c/include/ipc/loc.h
+pub type service_id_t = sysarg_t;
+
+// uspace/lib/c/include/ipc/vfs.h
+pub type fs_handle_t = i16;
+pub type fs_index_t = u32;
+
+// uspace/lib/c/include/offset.h
+pub type aoff64_t = u64;
+
+// uspace/lib/c/include/time.h
+pub type time_t = c_longlong;
+pub type usec_t = c_longlong;
+
+// uspace/lib/inet/include/inet/addr.h
+pub type addr32_t = u32;
+pub type addr128_t = [u8; 16];
+
+// uspace/lib/posix/include/posix/pthread.h
+pub type pthread_key_t = c_int;
+
+// uspace/lib/posix/include/posix/sys/types.h
+pub type clockid_t = c_int;
+pub type pid_t = c_int;
+
+s! {
+    // common/include/adt/list.h
+    pub struct link_t {
+        pub next: *mut link_t,
+        pub prev: *mut link_t,
+    }
+
+    pub struct list_t {
+        pub head: link_t,
+    }
+
+    // uspace/lib/c/include/dirent.h
+    pub struct dirent {
+        pub d_name: [c_char; 256],
+    }
+
+    // uspace/lib/c/include/fibril.h
+    pub struct fibril_owner_info_t {
+        pub owned_by: *mut fibril_t,
+    }
+
+    // uspace/lib/c/include/fibril_synch.h
+    pub struct fibril_mutex_t {
+        pub oi: fibril_owner_info_t,
+        pub counter: c_int,
+        pub waiters: list_t,
+    }
+
+    pub struct fibril_condvar_t {
+        pub waiters: list_t,
+    }
+
+    // uspace/lib/c/include/time.h
+    pub struct timespec {
+        pub tv_sec: time_t,
+        pub tv_nsec: c_long,
+    }
+
+    // uspace/lib/c/include/vfs/vfs.h
+    pub struct vfs_stat_t {
+        pub fs_handle: fs_handle_t,
+        pub service_id: service_id_t,
+        pub index: fs_index_t,
+        pub lnkcnt: c_uint,
+        pub is_file: bool,
+        pub is_directory: bool,
+        pub size: aoff64_t,
+        pub service: service_id_t,
+    }
+
+    // uspace/lib/inet/include/inet/dnsr.h
+    pub struct dnsr_hostinfo_t {
+        pub cname: *mut c_char,
+        pub addr: inet_addr_t,
+    }
+
+    // uspace/lib/inet/include/inet/endpoint.h
+    pub struct inet_ep2_t {
+        pub local_link: service_id_t,
+        pub local: inet_ep_t,
+        pub remote: inet_ep_t,
+    }
+
+    pub struct inet_ep_t {
+        pub addr: inet_addr_t,
+        pub port: u16,
+    }
+
+    // uspace/lib/inet/include/inet/tcp.h
+    pub struct tcp_cb_t {
+        pub connected: extern "C" fn(conn: *mut tcp_conn_t),
+        pub conn_failed: extern "C" fn(conn: *mut tcp_conn_t),
+        pub conn_reset: extern "C" fn(conn: *mut tcp_conn_t),
+        pub data_avail: extern "C" fn(conn: *mut tcp_conn_t),
+        pub urg_data: extern "C" fn(conn: *mut tcp_conn_t),
+    }
+    pub struct tcp_listen_cb_t {
+        pub new_conn: extern "C" fn(listener: *mut tcp_listener_t, conn: *mut tcp_conn_t),
+    }
+}
+
+// uspace/lib/inet/include/inet/addr.h
+e! {
+    #[repr(u32)]
+    pub enum ip_ver_t {
+        ip_any,
+        ip_v4,
+        ip_v6,
+    }
+}
+
+// uspace/lib/inet/include/inet/addr.h
+s_no_extra_traits! {
+    pub union __inet_addr_t_addr_union {
+        pub addr: addr32_t,
+        pub addr6: addr128_t,
+    }
+
+    pub struct inet_addr_t {
+        pub version: ip_ver_t,
+        pub addr: __inet_addr_t_addr_union,
+    }
+}
+
+// abi/include/abi/errno.h
+pub const EOK: errno_t = 0;
+pub const ENOENT: errno_t = 1;
+pub const ENOMEM: errno_t = 2;
+pub const ELIMIT: errno_t = 3;
+pub const EREFUSED: errno_t = 4;
+pub const EFORWARD: errno_t = 5;
+pub const EPERM: errno_t = 6;
+pub const EHANGUP: errno_t = 7;
+pub const EPARTY: errno_t = 8;
+pub const EEXIST: errno_t = 9;
+pub const EBADMEM: errno_t = 10;
+pub const ENOTSUP: errno_t = 11;
+pub const EADDRNOTAVAIL: errno_t = 12;
+pub const ETIMEOUT: errno_t = 13;
+pub const EINVAL: errno_t = 14;
+pub const EBUSY: errno_t = 15;
+pub const EOVERFLOW: errno_t = 16;
+pub const EINTR: errno_t = 17;
+pub const EMFILE: errno_t = 18;
+pub const ENAMETOOLONG: errno_t = 19;
+pub const EISDIR: errno_t = 20;
+pub const ENOTDIR: errno_t = 21;
+pub const ENOSPC: errno_t = 22;
+pub const ENOTEMPTY: errno_t = 23;
+pub const EBADF: errno_t = 24;
+pub const EDOM: errno_t = 25;
+pub const ERANGE: errno_t = 26;
+pub const EXDEV: errno_t = 27;
+pub const EIO: errno_t = 28;
+pub const EMLINK: errno_t = 29;
+pub const ENXIO: errno_t = 30;
+pub const ENOFS: errno_t = 31;
+pub const EBADCHECKSUM: errno_t = 32;
+pub const ESTALL: errno_t = 33;
+pub const EEMPTY: errno_t = 34;
+pub const ENAK: errno_t = 35;
+pub const EAGAIN: errno_t = 36;
+
+// uspace/lib/posix/include/posix/time.h
+pub const CLOCK_REALTIME: clockid_t = 0;
+
+// uspace/lib/c/include/stdio.h
+pub const SEEK_SET: c_int = 0;
+pub const SEEK_CUR: c_int = 1;
+pub const SEEK_END: c_int = 2;
+
+// 'static inline' functions from libc
+// common/include/adt/list.h
+f! {
+    pub fn list_initialize(list: *mut list_t) -> () {
+        let list = &mut *list;
+        list.head.next = &mut list.head;
+        list.head.prev = &mut list.head;
+    }
+
+    // uspace/lib/c/include/fibril_synch.h
+    pub fn fibril_mutex_initialize(fm: *mut fibril_mutex_t) -> () {
+        let fm = &mut *fm;
+        fm.oi.owned_by = core::ptr::null_mut();
+        fm.counter = 1;
+        list_initialize(&mut fm.waiters);
+    }
+}
+
+missing! {
+    // uspace/lib/c/include/dirent.h
+    #[cfg_attr(feature = "extra_traits", derive(Debug))]
+    pub enum DIR {}
+
+    // uspace/lib/c/include/fibril.h
+    #[cfg_attr(feature = "extra_traits", derive(Debug))]
+    pub enum fibril_t {}
+
+    // uspace/lib/c/include/stdio.h
+    #[cfg_attr(feature = "extra_traits", derive(Debug))]
+    pub enum FILE {}
+
+    // uspace/lib/inet/include/inet/tcp.h
+    #[cfg_attr(feature = "extra_traits", derive(Debug))]
+    pub enum tcp_t {}
+    #[cfg_attr(feature = "extra_traits", derive(Debug))]
+    pub enum tcp_conn_t {}
+    #[cfg_attr(feature = "extra_traits", derive(Debug))]
+    pub enum tcp_listener_t {}
+}
+
+#[link(name = "c")]
+#[link(name = "posix")]
+#[link(name = "inet")]
+// FIXME: libstartfiles is a static library. But when we explicitly add `kind="static"` below, we an error
+// when building libc that says "could not find native static library `startfiles`, perhaps an -L flag is missing?"
+// It happens due to this piece of code:
+// https://github.com/rust-lang/rust/blob/1de931283df18f3af4922fe9a96adcc8936ac42e/compiler/rustc_codegen_ssa/src/back/link.rs#L370
+// When building .rlib, Rust doesn't invoke the native linker (which we specify in rustc_target), but instead
+// tries to find all the libraries by itself. And I suppose it doesn't learn the link search paths from
+// the linker.
+#[link(name = "startfiles")]
+extern "C" {}
+
+extern "C" {
+    // common/include/stdlib.h
+    pub fn malloc(size: usize) -> *mut c_void;
+    pub fn calloc(nmemb: usize, size: usize) -> *mut c_void;
+    pub fn realloc(addr: *mut c_void, size: usize) -> *mut c_void;
+    pub fn free(addr: *mut c_void);
+
+    pub fn memalign(align: usize, size: usize) -> *mut c_void;
+
+    pub fn rand() -> c_int;
+    pub fn srand(seed: c_uint);
+
+    pub fn exit(code: c_int) -> !;
+    pub fn abort() -> !;
+
+    pub fn getenv(env: *const c_char) -> *mut c_char;
+
+    // common/include/str_error.h
+    pub fn str_error(err: errno_t) -> *const c_char;
+    pub fn str_error_name(err: errno_t) -> *const c_char;
+
+    // uspace/lib/c/include/dirent.h
+    pub fn opendir(name: *const c_char) -> *mut DIR;
+    pub fn readdir(dir: *mut DIR) -> *mut dirent;
+    pub fn closedir(dir: *mut DIR) -> c_int;
+    pub fn rewinddir(dir: *mut DIR);
+
+    // uspace/lib/c/include/errno.h
+    pub fn __errno() -> *mut errno_t;
+
+    // uspace/lib/c/include/fibril.h
+    pub fn fibril_create_generic(
+        func: extern "C" fn(*mut c_void) -> errno_t,
+        arg: *mut c_void,
+        stacksize: size_t,
+    ) -> fid_t;
+    pub fn fibril_start(f: fid_t);
+    pub fn fibril_exit(retval: c_long) -> !;
+    pub fn fibril_detach(f: fid_t);
+    pub fn fibril_yield();
+    pub fn fibril_usleep(usec: usec_t);
+    pub fn fibril_get_id() -> fid_t;
+
+    // uspace/lib/c/include/fibril_synch.h
+    pub fn fibril_mutex_lock(mutex: *mut fibril_mutex_t);
+    pub fn fibril_mutex_unlock(mutex: *mut fibril_mutex_t);
+    pub fn fibril_mutex_trylock(mutex: *mut fibril_mutex_t) -> bool;
+    pub fn fibril_mutex_is_locked(mutex: *mut fibril_mutex_t) -> bool;
+
+    pub fn fibril_condvar_initialize(condvar: *mut fibril_condvar_t);
+    pub fn fibril_condvar_wait(condvar: *mut fibril_condvar_t, mutex: *mut fibril_mutex_t);
+    pub fn fibril_condvar_wait_timeout(
+        condvar: *mut fibril_condvar_t,
+        mutex: *mut fibril_mutex_t,
+        timeout: usec_t,
+    ) -> errno_t;
+    pub fn fibril_condvar_signal(condvar: *mut fibril_condvar_t);
+    pub fn fibril_condvar_broadcast(condvar: *mut fibril_condvar_t);
+
+    // uspace/lib/c/include/stdio.h
+    pub static stdin: *mut FILE;
+    pub static stdout: *mut FILE;
+    pub static stderr: *mut FILE;
+
+    pub fn fputc(c: c_int, stream: *mut FILE) -> c_int;
+    pub fn fputs(s: *const c_char, stream: *mut FILE) -> c_int;
+
+    pub fn fopen(filename: *const c_char, mode: *const c_char) -> *mut FILE;
+    pub fn fclose(stream: *mut FILE) -> c_int;
+    pub fn fflush(stream: *mut FILE) -> c_int;
+
+    pub fn fread(buf: *mut c_void, size: size_t, nmemb: size_t, stream: *mut FILE) -> size_t;
+    pub fn fwrite(buf: *const c_void, size: size_t, nmemb: size_t, stream: *mut FILE) -> size_t;
+
+    pub fn fseek(stream: *mut FILE, offset: c_long, whence: c_int) -> c_int;
+    pub fn ftell(stream: *mut FILE) -> c_long;
+
+    pub fn fileno(stream: *mut FILE) -> c_int;
+
+    // uspace/lib/c/include/time.h
+    pub fn getuptime(tp: *mut timespec);
+
+    // uspace/lib/c/include/vfs/vfs.h
+    pub fn vfs_stat_path(path: *const c_char, stat: *mut vfs_stat_t) -> errno_t;
+
+    // uspace/lib/inet/include/inet/dnsr.h
+    pub fn dnsr_name2host(
+        name: *const c_char,
+        info: *mut *mut dnsr_hostinfo_t,
+        ipver: ip_ver_t,
+    ) -> errno_t;
+    pub fn dnsr_hostinfo_destroy(info: *mut dnsr_hostinfo_t);
+
+    // uspace/lib/inet/include/inet/endpoint.h
+    pub fn inet_ep_init(ep: *mut inet_ep_t);
+    pub fn inet_ep2_init(epp: *mut inet_ep2_t);
+
+    // uspace/lib/inet/include/inet/tcp.h
+    pub fn tcp_create(tcp: *mut *mut tcp_t) -> errno_t;
+    pub fn tcp_destroy(tcp: *mut tcp_t);
+
+    pub fn tcp_conn_create(
+        tcp: *mut tcp_t,
+        epp: *mut inet_ep2_t,
+        callbacks: *mut tcp_cb_t,
+        arg: *mut c_void,
+        conn: *mut *mut tcp_conn_t,
+    ) -> errno_t;
+    pub fn tcp_conn_destroy(conn: *mut tcp_conn_t);
+
+    pub fn tcp_listener_create(
+        tcp: *mut tcp_t,
+        ep: *mut inet_ep_t,
+        listen_callbacks: *mut tcp_listen_cb_t,
+        listen_arg: *mut c_void,
+        conn_callbacks: *mut tcp_cb_t,
+        conn_arg: *mut c_void,
+        listener: *mut *mut tcp_listener_t,
+    ) -> errno_t;
+    pub fn tcp_listener_destroy(listener: *mut tcp_listener_t);
+
+    pub fn tcp_conn_userptr(conn: *mut tcp_conn_t) -> *mut c_void;
+    pub fn tcp_listener_userptr(listener: *mut tcp_listener_t) -> *mut c_void;
+
+    pub fn tcp_conn_wait_connected(conn: *mut tcp_conn_t) -> errno_t;
+    pub fn tcp_conn_send(conn: *mut tcp_conn_t, buf: *const c_void, len: size_t) -> errno_t;
+    pub fn tcp_conn_send_fin(conn: *mut tcp_conn_t) -> errno_t;
+    pub fn tcp_conn_push(conn: *mut tcp_conn_t) -> errno_t;
+    pub fn tcp_conn_reset(conn: *mut tcp_conn_t) -> errno_t;
+
+    pub fn tcp_conn_recv(
+        conn: *mut tcp_conn_t,
+        buf: *mut c_void,
+        bufsize: size_t,
+        received_len: *mut size_t,
+    ) -> errno_t;
+    pub fn tcp_conn_recv_wait(
+        conn: *mut tcp_conn_t,
+        buf: *mut c_void,
+        bufsize: size_t,
+        received_len: *mut size_t,
+    ) -> errno_t;
+
+    // uspace/lib/posix/include/posix/pthread.h
+    pub fn pthread_key_create(
+        key: *mut pthread_key_t,
+        destructor: unsafe extern "C" fn(*mut c_void),
+    ) -> c_int;
+    pub fn pthread_getspecific(key: pthread_key_t) -> *mut c_void;
+    pub fn pthread_setspecific(key: pthread_key_t, value: *const c_void) -> c_int;
+    pub fn pthread_key_delete(key: pthread_key_t) -> c_int;
+
+    // uspace/lib/posix/include/posix/time.h
+    pub fn clock_getres(clock_id: clockid_t, res: *mut timespec) -> c_int;
+    pub fn clock_gettime(clock_id: clockid_t, tp: *mut timespec) -> c_int;
+    pub fn clock_settime(clock_id: clockid_t, tp: *const timespec) -> c_int;
+    pub fn clock_nanosleep(
+        clock_id: clockid_t,
+        flags: c_int,
+        rqtp: *const timespec,
+        rmtp: *mut timespec,
+    ) -> c_int;
+
+    // uspace/lib/posix/include/posix/unistd.h
+    pub fn getpid() -> pid_t;
+    pub fn getcwd(buf: *mut c_char, size: size_t) -> *mut c_char;
+    pub fn chdir(buf: *const c_char) -> c_int;
+    pub static environ: *const *const c_char;
+    pub fn isatty(fd: c_int) -> c_int;
+}
diff --git a/src/lib.rs b/src/lib.rs
index 255f4550056ce..c136b57d03b8f 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -86,6 +86,14 @@ cfg_if! {
         mod unix;
         pub use crate::unix::*;
 
+        prelude!();
+    } else if #[cfg(target_os = "helenos")] {
+        mod primitives;
+        pub use primitives::*;
+
+        mod helenos;
+        pub use self::helenos::*;
+
         prelude!();
     } else if #[cfg(target_os = "hermit")] {
         mod primitives;