diff --git a/include/crash.h b/include/crash.h
new file mode 100644
index 0000000..788fd48
--- /dev/null
+++ b/include/crash.h
@@ -0,0 +1,6 @@
+#ifndef ANT_CRASH_H
+#define ANT_CRASH_H
+
+void ant_crash_init(void);
+
+#endif
diff --git a/src/crash.c b/src/crash.c
new file mode 100644
index 0000000..a4f0d02
--- /dev/null
+++ b/src/crash.c
@@ -0,0 +1,149 @@
+#include <compat.h> // IWYU pragma: keep
+#include "crash.h"
+
+#include <stdio.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+#ifndef _WIN32
+#include <signal.h>
+
+#define ANT_CRASH_ALT_STACK_SIZE (64 * 1024)
+
+#if defined(__APPLE__) || defined(__linux__) || defined(__GLIBC__)
+#define ANT_CRASH_HAVE_EXECINFO 1
+#include <execinfo.h>
+#endif
+
+static void as_write(int fd, const char *s) {
+  size_t len = 0;
+  while (s[len]) len++;
+  ssize_t _ = write(fd, s, len);
+  (void)_;
+}
+
+static void as_write_uint(int fd, unsigned long v) {
+  char buf[32];
+  int i = (int)sizeof(buf);
+  buf[--i] = '\0';
+  if (v == 0) buf[--i] = '0';
+  while (v && i > 0) {
+    buf[--i] = (char)('0' + (v % 10));
+    v /= 10;
+  }
+  as_write(fd, &buf[i]);
+}
+
+static int install_altstack(void) {
+#ifdef SA_ONSTACK
+  static void *stack_mem;
+  if (stack_mem) return 1;
+
+  stack_mem = malloc(ANT_CRASH_ALT_STACK_SIZE);
+  if (!stack_mem) return 0;
+
+  stack_t ss;
+  memset(&ss, 0, sizeof(ss));
+  ss.ss_sp = stack_mem;
+  ss.ss_size = ANT_CRASH_ALT_STACK_SIZE;
+  ss.ss_flags = 0;
+
+  if (sigaltstack(&ss, NULL) == 0) return 1;
+
+  free(stack_mem);
+  stack_mem = NULL;
+#endif
+  return 0;
+}
+
+static const char *signal_name(int sig) {
+switch (sig) {
+  case SIGSEGV: return "SIGSEGV (invalid memory access)";
+  case SIGBUS:  return "SIGBUS (bus error)";
+  case SIGFPE:  return "SIGFPE (arithmetic exception)";
+  case SIGILL:  return "SIGILL (illegal instruction)";
+  case SIGABRT: return "SIGABRT (abort)";
+  default:      return "fatal signal";
+}}
+
+static void crash_handler(int sig, siginfo_t *info, void *ucontext) {
+  struct sigaction dfl;
+  memset(&dfl, 0, sizeof(dfl));
+  
+  dfl.sa_handler = SIG_DFL;
+  sigemptyset(&dfl.sa_mask);
+  sigaction(sig, &dfl, NULL);
+
+  int fd = STDERR_FILENO;
+  as_write(fd, "\n=== ant crashed: ");
+  as_write(fd, signal_name(sig));
+  as_write(fd, " (signal ");
+  as_write_uint(fd, (unsigned long)sig);
+  as_write(fd, ") ===\n");
+
+  if (info) {
+    as_write(fd, "  fault address: 0x");
+    char hex[2 + sizeof(void *) * 2 + 1];
+    int hi = (int)sizeof(hex);
+    
+    hex[--hi] = '\0';
+    uintptr_t addr = (uintptr_t)info->si_addr;
+    
+    if (addr == 0) hex[--hi] = '0';
+    else while (addr && hi > 0) {
+      unsigned d = (unsigned)(addr & 0xF);
+      hex[--hi] = (char)(d < 10 ? '0' + d : 'a' + d - 10);
+      addr >>= 4;
+    }
+    
+    as_write(fd, &hex[hi]);
+    as_write(fd, "\n");
+  }
+
+  as_write(fd, "  ant version: " ANT_VERSION "\n");
+  as_write(fd, "  pid: ");
+  as_write_uint(fd, (unsigned long)getpid());
+  as_write(fd, "\n\nNative backtrace:\n");
+
+#ifdef ANT_CRASH_HAVE_EXECINFO
+  void *frames[64];
+  int n = backtrace(frames, (int)(sizeof(frames) / sizeof(frames[0])));
+  int skip = n > 2 ? 2 : 0;
+  if (skip) as_write(fd, "  (omitted crash_handler and signal trampoline frames)\n");
+  backtrace_symbols_fd(frames + skip, n - skip, fd);
+#else
+  as_write(fd, "  (no execinfo support on this platform)\n");
+#endif
+
+  as_write(fd,
+    "\nPlease report this at https://github.com/themackabu/ant/issues\n"
+    "Include the backtrace above and a minimal reproducer if possible.\n\n");
+
+  raise(sig);
+}
+
+void ant_crash_init(void) {
+  struct sigaction sa;
+  memset(&sa, 0, sizeof(sa));
+  sa.sa_sigaction = crash_handler;
+  sa.sa_flags = SA_SIGINFO | SA_RESETHAND;
+#ifdef SA_ONSTACK
+  if (install_altstack()) sa.sa_flags |= SA_ONSTACK;
+#endif
+  sigemptyset(&sa.sa_mask);
+
+  static const int sigs[] = { SIGSEGV, SIGBUS, SIGFPE, SIGILL, SIGABRT };
+  for (size_t i = 0; i < sizeof(sigs) / sizeof(sigs[0]); i++) {
+    sigaction(sigs[i], &sa, NULL);
+  }
+}
+
+#else // _WIN32
+
+void ant_crash_init(void) {
+  // TODO: SetUnhandledExceptionFilter + StackWalk64 / dbghelp
+}
+
+#endif
diff --git a/src/main.c b/src/main.c
index eefddf1..3cc9c08 100644
--- a/src/main.c
+++ b/src/main.c
@@ -10,6 +10,7 @@
 
 #include "ant.h"
 #include "gc.h"
+#include "crash.h"
 #include "repl.h"
 #include "debug.h"
 #include "utils.h"
@@ -378,6 +379,8 @@ static int execute_module(ant_t *js, const char *filename) {
 }
 
 int main(int argc, char *argv[]) {
+  if (!getenv("ANT_NO_CRASH_HANDLER")) ant_crash_init();
+  
   setup_console_colors();
   parse_ant_debug_flags();