diff --git a/kernel/CMakeLists.txt b/kernel/CMakeLists.txt
index 9f66d318..4f643a06 100644
--- a/kernel/CMakeLists.txt
+++ b/kernel/CMakeLists.txt
@@ -47,7 +47,7 @@ set(SOURCES
     src/sys/signal.cpp
     src/sys/socket.cpp
     src/sys/poll.cpp
-    src/sys/alarm.cpp
+    src/sys/setitimer.cpp
     src/sys/pledge.cpp
     src/sys/memstat.cpp
     src/fs/VFS.cpp
diff --git a/kernel/src/api/Syscall.h b/kernel/src/api/Syscall.h
index d85c6914..f05dd6fe 100644
--- a/kernel/src/api/Syscall.h
+++ b/kernel/src/api/Syscall.h
@@ -8,8 +8,8 @@
                     _e(umount) _e(pstat) _e(getrusage) _e(symlinkat) _e(readlinkat) _e(umask) _e(linkat) _e(faccessat) \
                         _e(pivot_root) _e(sigreturn) _e(sigaction) _e(kill) _e(sigprocmask) _e(setpgid) _e(isatty)     \
                             _e(getpgid) _e(socket) _e(bind) _e(connect) _e(listen) _e(accept) _e(poll) _e(msync)       \
-                                _e(truncate) _e(ftruncate) _e(utimensat) _e(alarm) _e(pledge) _e(memstat) _e(setsid)   \
-                                    _e(getsid)
+                                _e(truncate) _e(ftruncate) _e(utimensat) _e(setitimer) _e(pledge) _e(memstat)          \
+                                    _e(setsid) _e(getsid)
 
 enum Syscalls
 {
diff --git a/kernel/src/sys/alarm.cpp b/kernel/src/sys/alarm.cpp
deleted file mode 100644
index 652d08c1..00000000
--- a/kernel/src/sys/alarm.cpp
+++ /dev/null
@@ -1,35 +0,0 @@
-#include "Pledge.h"
-#include "sys/Syscall.h"
-#include "thread/Scheduler.h"
-#include "thread/Timer.h"
-#include <luna/Common.h>
-
-Result<u64> sys_alarm(Registers*, SyscallArgs args)
-{
-    unsigned int seconds = (unsigned int)args[0];
-
-    auto* current = Scheduler::current();
-
-    TRY(check_pledge(current, Promise::p_stdio));
-
-    Clock* clock = nullptr;
-
-    u64 ticks_left = current->timer ? current->timer->clock->ticks_left(current->timer) : 0;
-
-    if (current->timer)
-    {
-        clock = current->timer->clock;
-        if (clock) clock->remove_from_timer_queue(current->timer);
-    }
-    else
-        current->timer = TRY(make<Timer>());
-
-    if (!clock) clock = &g_realtime_clock;
-
-    current->timer->total_ticks = ceil_div((static_cast<long>(seconds) * 1'000'000'000), clock->resolution());
-    current->timer->thread = current;
-
-    clock->add_to_timer_queue(current->timer);
-
-    return (ticks_left * clock->resolution()) / 1'000'000'000;
-}
diff --git a/kernel/src/sys/exec.cpp b/kernel/src/sys/exec.cpp
index a86700f7..534e5aaa 100644
--- a/kernel/src/sys/exec.cpp
+++ b/kernel/src/sys/exec.cpp
@@ -107,6 +107,17 @@ Result<u64> sys_execve(Registers* regs, SyscallArgs args)
 
     guard.deactivate();
 
+    // Reset all timers.
+    if (current->real_timer.clock) { current->real_timer.clock->remove_from_timer_queue(&current->real_timer); }
+    if (current->virtual_timer.clock)
+    {
+        current->virtual_timer.clock->remove_from_timer_queue(&current->virtual_timer);
+    }
+    if (current->profiling_timer.clock)
+    {
+        current->profiling_timer.clock->remove_from_timer_queue(&current->profiling_timer);
+    }
+
     for (int i = 0; i < FD_MAX; i++)
     {
         auto& descriptor = current->fd_table[i];
@@ -173,6 +184,9 @@ Result<u64> sys_fork(Registers* regs, SyscallArgs)
     thread->pgid = current->pgid;
     thread->sid = current->sid;
 
+    thread->virtual_clock.set_resolution(1'000'000);
+    thread->profiling_clock.set_resolution(1'000'000);
+
     for (int i = 0; i < FD_MAX; i++) { thread->fd_table[i] = current->fd_table[i]; }
 
     image->apply(thread);
diff --git a/kernel/src/sys/setitimer.cpp b/kernel/src/sys/setitimer.cpp
new file mode 100644
index 00000000..422407c2
--- /dev/null
+++ b/kernel/src/sys/setitimer.cpp
@@ -0,0 +1,86 @@
+#define _TIMESPEC_MACROS_INCLUDED
+#include "Pledge.h"
+#include "memory/MemoryManager.h"
+#include "sys/Syscall.h"
+#include "thread/Scheduler.h"
+#include "thread/Timer.h"
+#include <bits/itimer.h>
+#include <luna/Common.h>
+
+Result<u64> sys_setitimer(Registers*, SyscallArgs args)
+{
+    int which = (int)args[0];
+    const struct itimerval* new_timer = (const struct itimerval*)args[1];
+    struct itimerval* old_timer = (struct itimerval*)args[2];
+
+    auto* current = Scheduler::current();
+
+    TRY(check_pledge(current, Promise::p_stdio));
+
+    Timer* timer;
+    Clock* clock;
+    switch (which)
+    {
+    case ITIMER_REAL:
+        timer = &current->real_timer;
+        clock = &g_realtime_clock;
+        break;
+    case ITIMER_VIRTUAL:
+        timer = &current->virtual_timer;
+        clock = &current->virtual_clock;
+        break;
+    case ITIMER_PROF:
+        timer = &current->profiling_timer;
+        clock = &current->profiling_clock;
+        break;
+    default: return err(EINVAL);
+    }
+
+    if (old_timer)
+    {
+        if (timer->clock)
+        {
+            struct itimerval result;
+            auto total = timer->clock->from_ticks(timer->total_ticks);
+            auto left = timer->clock->from_ticks(timer->clock->ticks_left(timer));
+            result.it_interval = TIMESPEC_TO_TIMEVAL(total);
+            result.it_value = TIMESPEC_TO_TIMEVAL(left);
+            if (!MemoryManager::copy_to_user_typed(old_timer, &result)) return err(EFAULT);
+        }
+        else
+        {
+            struct itimerval result;
+            memset(&result, 0, sizeof(result));
+            if (!MemoryManager::copy_to_user_typed(old_timer, &result)) return err(EFAULT);
+        }
+    }
+
+    if (new_timer)
+    {
+        if (timer->clock) timer->clock->remove_from_timer_queue(timer);
+
+        struct itimerval itimer;
+        if (!MemoryManager::copy_from_user_typed(new_timer, &itimer)) return err(EFAULT);
+
+        timer->signo = SIGALRM; // FIXME: Also use SIGVTALRM or SIGPROF for other timer types.
+        timer->thread = current;
+
+        if (itimer.it_interval.tv_sec != 0 || itimer.it_interval.tv_usec != 0)
+        {
+            timer->restart = true;
+            timer->total_ticks =
+                (itimer.it_interval.tv_sec * 1'000'000'000 + itimer.it_interval.tv_usec * 1000) / clock->resolution();
+        }
+        else
+            timer->restart = false;
+
+        if (itimer.it_value.tv_sec != 0 || itimer.it_value.tv_usec != 0)
+        {
+            timer->delta_ticks =
+                (itimer.it_value.tv_sec * 1'000'000'000 + itimer.it_value.tv_usec * 1000) / clock->resolution();
+            clock->add_to_timer_queue(timer);
+        }
+    }
+
+    return 0;
+}
diff --git a/kernel/src/thread/Clock.cpp b/kernel/src/thread/Clock.cpp
index edf72f16..ce8bce87 100644
--- a/kernel/src/thread/Clock.cpp
+++ b/kernel/src/thread/Clock.cpp
@@ -73,8 +73,6 @@ void Clock::add_to_timer_queue(Timer* timer)
 {
     check(timer->clock == nullptr);
 
-    timer->delta_ticks = timer->total_ticks;
-
     for (auto* t : m_timer_queue)
     {
         if (timer->delta_ticks <= t->delta_ticks)
@@ -159,3 +157,10 @@ u64 Clock::ticks_left(Timer* timer)
     }
     return total;
 }
+
+struct timespec Clock::from_ticks(u64 ticks)
+{
+    u64 nanoseconds = ticks * m_resolution;
+    return timespec { .tv_sec = static_cast<time_t>(nanoseconds / 1'000'000'000),
+                      .tv_nsec = static_cast<long>(nanoseconds % 1'000'000'000) };
+}
diff --git a/kernel/src/thread/Clock.h b/kernel/src/thread/Clock.h
index b2aaee56..e9653937 100644
--- a/kernel/src/thread/Clock.h
+++ b/kernel/src/thread/Clock.h
@@ -19,6 +19,8 @@ struct Clock
     void get_time(struct timespec& out);
     long resolution();
 
+    struct timespec from_ticks(u64 ticks);
+
     u64 ticks_left(Timer* timer);
 
   private:
diff --git a/kernel/src/thread/Scheduler.cpp b/kernel/src/thread/Scheduler.cpp
index 56be87ec..fcad36f7 100644
--- a/kernel/src/thread/Scheduler.cpp
+++ b/kernel/src/thread/Scheduler.cpp
@@ -102,6 +102,9 @@ namespace Scheduler
         thread->is_kernel = true;
         thread->active_directory = MMU::kernel_page_directory();
 
+        thread->virtual_clock.set_resolution(1'000'000);
+        thread->profiling_clock.set_resolution(1'000'000);
+
         thread->auth = Credentials { .uid = 0, .euid = 0, .suid = 0, .gid = 0, .egid = 0, .sgid = 0 };
 
         g_threads.append(thread);
@@ -217,11 +220,7 @@ namespace Scheduler
             MemoryManager::unmap_owned_and_free_vm(stack.bottom(), stack.bytes() / ARCH_PAGE_SIZE).release_value();
         }
 
-        if (thread->timer)
-        {
-            thread->timer->clock->remove_from_timer_queue(thread->timer);
-            delete thread->timer;
-        }
+        if (thread->real_timer.clock) { thread->real_timer.clock->remove_from_timer_queue(&thread->real_timer); }
 
         delete thread;
 
@@ -302,7 +301,12 @@ namespace Scheduler
 
         if (is_in_kernel(regs)) g_current->kernel_ticks_self++;
         else
+        {
+            g_current->virtual_clock.tick();
             g_current->user_ticks_self++;
+        }
+
+        g_current->profiling_clock.tick();
 
         g_current->ticks_left--;
 
diff --git a/kernel/src/thread/Thread.h b/kernel/src/thread/Thread.h
index f5767f34..0e9190ee 100644
--- a/kernel/src/thread/Thread.h
+++ b/kernel/src/thread/Thread.h
@@ -98,7 +98,12 @@ struct Thread : public LinkedListNode<Thread>
 
     mode_t umask { 0 };
 
-    Timer* timer { nullptr };
+    Timer real_timer;
+    Timer virtual_timer;
+    Timer profiling_timer;
+
+    Clock virtual_clock;
+    Clock profiling_clock;
 
     StaticString<128> cmdline;
 
diff --git a/kernel/src/thread/Timer.h b/kernel/src/thread/Timer.h
index f63942f3..bd1c1bf4 100644
--- a/kernel/src/thread/Timer.h
+++ b/kernel/src/thread/Timer.h
@@ -8,11 +8,11 @@ struct Clock;
 class Timer : public LinkedListNode<Timer>
 {
   public:
-    u64 delta_ticks;
-    u64 total_ticks;
+    u64 delta_ticks { 0 };
+    u64 total_ticks { 0 };
     Thread* thread;
     int signo { SIGALRM };
     bool restart { false };
 
-    Clock* clock;
+    Clock* clock { nullptr };
 };
diff --git a/libc/include/bits/itimer.h b/libc/include/bits/itimer.h
new file mode 100644
index 00000000..2708a330
--- /dev/null
+++ b/libc/include/bits/itimer.h
@@ -0,0 +1,18 @@
+/* bits/itimer.h: Constants for setitimer() and getitimer(). */
+
+#ifndef _BITS_ITIMER_H
+#define _BITS_ITIMER_H
+
+#include <bits/timespec.h>
+
+#define ITIMER_REAL 0
+#define ITIMER_VIRTUAL 1
+#define ITIMER_PROF 2
+
+struct itimerval
+{
+    struct timeval it_interval;
+    struct timeval it_value;
+};
+
+#endif
diff --git a/libc/include/bits/timespec.h b/libc/include/bits/timespec.h
index 66ec4dfa..4a1896cb 100644
--- a/libc/include/bits/timespec.h
+++ b/libc/include/bits/timespec.h
@@ -33,4 +33,13 @@ struct timeval
         }                                                                                                              \
     } while (0);
 #endif
+
+#define TIMEVAL_TO_TIMESPEC(x)                                                                                         \
+    {                                                                                                                  \
+        .tv_sec = (x).tv_sec, .tv_nsec = (x).tv_usec * 1000                                                            \
+    }
+#define TIMESPEC_TO_TIMEVAL(x)                                                                                         \
+    {                                                                                                                  \
+        .tv_sec = (x).tv_sec, .tv_usec = (x).tv_nsec / 1000                                                            \
+    }
 #endif
diff --git a/libc/include/sys/time.h b/libc/include/sys/time.h
index e29720b8..5b4bf915 100644
--- a/libc/include/sys/time.h
+++ b/libc/include/sys/time.h
@@ -6,6 +6,7 @@
 #define _INCLUDE_TIMESPEC_MACROS
 
 #include <bits/attrs.h>
+#include <bits/itimer.h>
 #include <bits/timespec.h>
 
 #ifdef __cplusplus
@@ -25,6 +26,9 @@ extern "C"
     /* Change a symlink's access and modification timestamps, with microsecond precision. */
     int lutimes(const char* path, const struct timeval buf[2]);
 
+    /* Set an interval timer. */
+    int setitimer(int which, const struct itimerval* new_timer, struct itimerval* old_timer);
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/libc/src/time.cpp b/libc/src/time.cpp
index 7f13646a..3f2bb102 100644
--- a/libc/src/time.cpp
+++ b/libc/src/time.cpp
@@ -200,4 +200,10 @@ extern "C"
 
         return ru.ru_utime.tv_sec * CLOCKS_PER_SEC + ru.ru_utime.tv_usec;
     }
+
+    int setitimer(int which, const struct itimerval* new_timer, struct itimerval* old_timer)
+    {
+        long rc = syscall(SYS_setitimer, which, new_timer, old_timer);
+        __errno_return(rc, int);
+    }
 }
diff --git a/libc/src/unistd.cpp b/libc/src/unistd.cpp
index c856635c..bb54e0ee 100644
--- a/libc/src/unistd.cpp
+++ b/libc/src/unistd.cpp
@@ -11,6 +11,7 @@
 #include <sys/mman.h>
 #include <sys/stat.h>
 #include <sys/syscall.h>
+#include <sys/time.h>
 #include <sys/utsname.h>
 #include <unistd.h>
 
@@ -519,7 +520,12 @@ extern "C"
 
     unsigned int alarm(unsigned int seconds)
     {
-        return (unsigned int)syscall(SYS_alarm, seconds);
+        struct itimerval old_value;
+        struct itimerval new_value;
+        memset(&new_value, 0, sizeof(new_value));
+        new_value.it_value.tv_sec = seconds;
+        if (setitimer(ITIMER_REAL, &new_value, &old_value) < 0) return 0;
+        return (unsigned int)old_value.it_value.tv_sec;
     }
 
     int pledge(const char* promises, const char* execpromises)