diff --git a/test/common.py b/test/common.py
index d5f6b70456d26..a98262e036fd9 100644
--- a/test/common.py
+++ b/test/common.py
@@ -202,6 +202,14 @@ def is_firefox():
   return EMTEST_BROWSER and 'firefox' in EMTEST_BROWSER.lower()
 
 
+def get_browser_config():
+  if is_chrome():
+    return ChromeConfig()
+  elif is_firefox():
+    return FirefoxConfig()
+  return None
+
+
 def compiler_for(filename, force_c=False):
   if shared.suffix(filename) in ('.cc', '.cxx', '.cpp') and not force_c:
     return EMXX
@@ -2413,11 +2421,7 @@ def configure_test_browser():
     EMTEST_BROWSER = '"' + EMTEST_BROWSER.replace("\\", "\\\\") + '"'
 
   if EMTEST_BROWSER_AUTO_CONFIG:
-    config = None
-    if is_chrome():
-      config = ChromeConfig()
-    elif is_firefox():
-      config = FirefoxConfig()
+    config = get_browser_config()
     if config:
       EMTEST_BROWSER += ' ' + ' '.join(config.default_flags)
       if EMTEST_HEADLESS == 1:
@@ -2438,6 +2442,22 @@ def list_processes_by_name(exe_name):
   return pids
 
 
+def terminate_list_of_processes(proc_list):
+  for proc in proc_list:
+    try:
+      proc.terminate()
+      # If the browser doesn't shut down gracefully (in response to SIGTERM)
+      # after 2 seconds kill it with force (SIGKILL).
+      try:
+        proc.wait(2)
+      except (subprocess.TimeoutExpired, psutil.TimeoutExpired):
+        logger.info('Browser did not respond to `terminate`.  Using `kill`')
+        proc.kill()
+        proc.wait()
+    except (psutil.NoSuchProcess, ProcessLookupError):
+      pass
+
+
 class FileLock:
   """Implements a filesystem-based mutex, with an additional feature that it
   returns an integer counter denoting how many times the lock has been locked
@@ -2522,19 +2542,7 @@ def __init__(self, *args, **kwargs):
 
   @classmethod
   def browser_terminate(cls):
-    for proc in cls.browser_procs:
-      try:
-        proc.terminate()
-        # If the browser doesn't shut down gracefully (in response to SIGTERM)
-        # after 2 seconds kill it with force (SIGKILL).
-        try:
-          proc.wait(2)
-        except (subprocess.TimeoutExpired, psutil.TimeoutExpired):
-          logger.info('Browser did not respond to `terminate`.  Using `kill`')
-          proc.kill()
-          proc.wait()
-      except (psutil.NoSuchProcess, ProcessLookupError):
-        pass
+    terminate_list_of_processes(cls.browser_procs)
 
   @classmethod
   def browser_restart(cls):
@@ -2567,11 +2575,8 @@ def browser_open(cls, url):
       # Recreate the new data directory.
       os.mkdir(browser_data_dir)
 
-      if is_chrome():
-        config = ChromeConfig()
-      elif is_firefox():
-        config = FirefoxConfig()
-      else:
+      config = get_browser_config()
+      if not config:
         exit_with_error(f'EMTEST_BROWSER_AUTO_CONFIG only currently works with firefox or chrome. EMTEST_BROWSER was "{EMTEST_BROWSER}"')
       if WINDOWS:
         # Escape directory delimiter backslashes for shlex.split.
diff --git a/test/runner.py b/test/runner.py
index ce76aba756863..6999c2a2276f7 100755
--- a/test/runner.py
+++ b/test/runner.py
@@ -488,6 +488,7 @@ def parse_args():
                            'Useful when combined with --failfast')
   parser.add_argument('--force64', action='store_true')
   parser.add_argument('--crossplatform-only', action='store_true')
+  parser.add_argument('--force-browser-process-termination', action='store_true', help='If true, a fail-safe method is used to ensure that all browser processes are terminated before and after the test suite run. Note that this option will terminate all browser processes, not just those launched by the harness, so will result in loss of all open browsing sessions.')
   parser.add_argument('--repeat', type=int, default=1,
                       help='Repeat each test N times (default: 1).')
   parser.add_argument('--bell', action='store_true', help='Play a sound after the test suite finishes.')
@@ -566,6 +567,18 @@ def set_env(name, option_value):
   utils.delete_file(common.flaky_tests_log_filename)
   utils.delete_file(common.browser_spawn_lock_filename)
   utils.delete_file(f'{common.browser_spawn_lock_filename}_counter')
+  if options.force_browser_process_termination or os.getenv('EMTEST_FORCE_BROWSER_PROCESS_TERMINATION'):
+    config = common.get_browser_config()
+
+    def terminate_all_browser_processes():
+      procs = common.list_processes_by_name(config.executable_name)
+      if len(procs) > 0:
+        print(f'Terminating {len(procs)} stray browser processes.')
+        common.terminate_list_of_processes(procs)
+
+    if config and hasattr(config, 'executable_name'):
+      atexit.register(terminate_all_browser_processes)
+      terminate_all_browser_processes()
 
   def prepend_default(arg):
     if arg.startswith('test_'):