diff --git a/changelog/3085.removal.rst b/changelog/3085.removal.rst
new file mode 100644
index 000000000..67ba04c28
--- /dev/null
+++ b/changelog/3085.removal.rst
@@ -0,0 +1,3 @@
+Removed support for passing strings to ``pytest.main``. Now, always pass a list of strings instead.
+
+See our `docs <https://docs.pytest.org/en/latest/deprecations.html#passing-command-line-string-to-pytest-main>`__ on information on how to update your code.
diff --git a/doc/en/deprecations.rst b/doc/en/deprecations.rst
index d814b0bee..6ec80cbe8 100644
--- a/doc/en/deprecations.rst
+++ b/doc/en/deprecations.rst
@@ -193,27 +193,6 @@ To update the code, use ``pytest.param``:
 
 
 
-Passing command-line string to ``pytest.main()``
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-
-.. deprecated:: 3.0
-
-Passing a command-line string to ``pytest.main()`` is deprecated:
-
-.. code-block:: python
-
-    pytest.main("-v -s")
-
-Pass a list instead:
-
-.. code-block:: python
-
-    pytest.main(["-v", "-s"])
-
-
-By passing a string, users expect that pytest will interpret that command-line using the shell rules they are working
-on (for example ``bash`` or ``Powershell``), but this is very hard/impossible to do in a portable way.
-
 
 [pytest] section in setup.cfg files
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
@@ -353,6 +332,30 @@ Change to:
     def test_foo(record_property):
         ...
 
+
+Passing command-line string to ``pytest.main()``
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+*Removed in version 4.0.*
+
+Passing a command-line string to ``pytest.main()`` is deprecated:
+
+.. code-block:: python
+
+    pytest.main("-v -s")
+
+Pass a list instead:
+
+.. code-block:: python
+
+    pytest.main(["-v", "-s"])
+
+
+By passing a string, users expect that pytest will interpret that command-line using the shell rules they are working
+on (for example ``bash`` or ``Powershell``), but this is very hard/impossible to do in a portable way.
+
+
+
 ``yield`` tests
 ~~~~~~~~~~~~~~~
 
diff --git a/src/_pytest/config/__init__.py b/src/_pytest/config/__init__.py
index 3ed82694b..d68b1249e 100644
--- a/src/_pytest/config/__init__.py
+++ b/src/_pytest/config/__init__.py
@@ -173,12 +173,9 @@ def _prepareconfig(args=None, plugins=None):
     elif isinstance(args, py.path.local):
         args = [str(args)]
     elif not isinstance(args, (tuple, list)):
-        if not isinstance(args, str):
-            raise ValueError("not a string or argument list: %r" % (args,))
-        args = shlex.split(args, posix=sys.platform != "win32")
-        from _pytest import deprecated
+        msg = "`args` parameter expected to be a list or tuple of strings, got: {!r} (type: {})"
+        raise TypeError(msg.format(args, type(args)))
 
-        warning = deprecated.MAIN_STR_ARGS
     config = get_config()
     pluginmanager = config.pluginmanager
     try:
diff --git a/src/_pytest/deprecated.py b/src/_pytest/deprecated.py
index 1de42924d..8b2fbf3f9 100644
--- a/src/_pytest/deprecated.py
+++ b/src/_pytest/deprecated.py
@@ -17,11 +17,6 @@ from _pytest.warning_types import RemovedInPytest4Warning
 from _pytest.warning_types import UnformattedWarning
 
 
-MAIN_STR_ARGS = RemovedInPytest4Warning(
-    "passing a string to pytest.main() is deprecated, "
-    "pass a list of arguments instead."
-)
-
 YIELD_TESTS = "yield tests were removed in pytest 4.0 - {name} will be ignored"
 
 
diff --git a/testing/acceptance_test.py b/testing/acceptance_test.py
index 0b7af5338..7276445ac 100644
--- a/testing/acceptance_test.py
+++ b/testing/acceptance_test.py
@@ -559,12 +559,11 @@ class TestInvocationVariants(object):
     def test_equivalence_pytest_pytest(self):
         assert pytest.main == py.test.cmdline.main
 
-    def test_invoke_with_string(self, capsys):
-        retcode = pytest.main("-h")
-        assert not retcode
-        out, err = capsys.readouterr()
-        assert "--help" in out
-        pytest.raises(ValueError, lambda: pytest.main(0))
+    def test_invoke_with_invalid_type(self, capsys):
+        with pytest.raises(
+            TypeError, match="expected to be a list or tuple of strings, got: '-h'"
+        ):
+            pytest.main("-h")
 
     def test_invoke_with_path(self, tmpdir, capsys):
         retcode = pytest.main(tmpdir)
diff --git a/testing/deprecated_test.py b/testing/deprecated_test.py
index b971a9d2e..5f5b78032 100644
--- a/testing/deprecated_test.py
+++ b/testing/deprecated_test.py
@@ -40,25 +40,6 @@ def test_pytest_custom_cfg_deprecated(testdir):
     )
 
 
-def test_str_args_deprecated(tmpdir):
-    """Deprecate passing strings to pytest.main(). Scheduled for removal in pytest-4.0."""
-    from _pytest.main import EXIT_NOTESTSCOLLECTED
-
-    warnings = []
-
-    class Collect(object):
-        def pytest_warning_captured(self, warning_message):
-            warnings.append(str(warning_message.message))
-
-    ret = pytest.main("%s -x" % tmpdir, plugins=[Collect()])
-    msg = (
-        "passing a string to pytest.main() is deprecated, "
-        "pass a list of arguments instead."
-    )
-    assert msg in warnings
-    assert ret == EXIT_NOTESTSCOLLECTED
-
-
 def test_getfuncargvalue_is_deprecated(request):
     pytest.deprecated_call(request.getfuncargvalue, "tmpdir")