diff --git a/documentation/url_handlers.rst b/documentation/url_handlers.rst
index b4f0da7..f8b1698 100644
--- a/documentation/url_handlers.rst
+++ b/documentation/url_handlers.rst
@@ -16,6 +16,7 @@
 - ``hwgrep://<regexp>[&skip_busy][&n=N]``
 - ``spy://port[?option[=value][&option[=value]]]``
 - ``alt://port?class=<classname>``
+- ``cp2110://<bus>:<dev>:<if>``
 
 .. versionchanged:: 3.0 Options are specified with ``?`` and ``&`` instead of ``/``
 
@@ -235,6 +236,21 @@
 
 .. versionadded:: 3.0
 
+``cp2110://``
+=============
+
+This backend implements support for HID-to-UART devices manufactured by Silicon
+Labs and marketed as CP2110 and CP2114. The implementation is (mostly)
+OS-independent and in userland. It relies on `cython-hidapi`_.
+
+.. _cython-hidapi: https://github.com/trezor/cython-hidapi
+
+Examples::
+
+    cp2110://0001:004a:00
+    cp2110://0002:0077:00
+
+.. versionadded:: 3.5
 
 Examples
 ========
@@ -247,5 +263,5 @@
 - ``hwgrep://0451:f432`` (USB VID:PID)
 - ``spy://COM54?file=log.txt``
 - ``alt:///dev/ttyUSB0?class=PosixPollSerial``
-
+- ``cp2110://0001:004a:00``
 
diff --git a/serial/urlhandler/protocol_cp2110.py b/serial/urlhandler/protocol_cp2110.py
new file mode 100644
index 0000000..04ba03e
--- /dev/null
+++ b/serial/urlhandler/protocol_cp2110.py
@@ -0,0 +1,258 @@
+#! python
+#
+# Backend for Silicon Labs CP2110/4 HID-to-UART devices.
+#
+# This file is part of pySerial. https://github.com/pyserial/pyserial
+# (C) 2001-2015 Chris Liechti <cliechti@gmx.net>
+# (C) 2019 Google LLC
+#
+# SPDX-License-Identifier:    BSD-3-Clause
+
+# This backend implements support for HID-to-UART devices manufactured
+# by Silicon Labs and marketed as CP2110 and CP2114. The
+# implementation is (mostly) OS-independent and in userland. It relies
+# on cython-hidapi (https://github.com/trezor/cython-hidapi).
+
+# The HID-to-UART protocol implemented by CP2110/4 is described in the
+# AN434 document from Silicon Labs:
+# https://www.silabs.com/documents/public/application-notes/AN434-CP2110-4-Interface-Specification.pdf
+
+# TODO items:
+
+# - rtscts support is configured for hardware flow control, but the
+#   signaling is missing (AN434 suggests this is done through GPIO).
+# - Cancelling reads and writes is not supported.
+# - Baudrate validation is not implemented, as it depends on model and configuration.
+
+import struct
+import threading
+
+try:
+    import urlparse
+except ImportError:
+    import urllib.parse as urlparse
+
+try:
+    import Queue
+except ImportError:
+    import queue as Queue
+
+import hid  # hidapi
+
+import serial
+from serial.serialutil import SerialBase, SerialException, portNotOpenError, to_bytes, Timeout
+
+
+# Report IDs and related constant
+_REPORT_GETSET_UART_ENABLE = 0x41
+_DISABLE_UART = 0x00
+_ENABLE_UART = 0x01
+
+_REPORT_SET_PURGE_FIFOS = 0x43
+_PURGE_TX_FIFO = 0x01
+_PURGE_RX_FIFO = 0x02
+
+_REPORT_GETSET_UART_CONFIG = 0x50
+
+_REPORT_SET_TRANSMIT_LINE_BREAK = 0x51
+_REPORT_SET_STOP_LINE_BREAK = 0x52
+
+
+class Serial(SerialBase):
+    # This is not quite correct. AN343 specifies that the minimum
+    # baudrate is different between CP2110 and CP2114, and it's halved
+    # when using non-8-bit symbols.
+    BAUDRATES = (300, 375, 600, 1200, 1800, 2400, 4800, 9600, 19200,
+                 38400, 57600, 115200, 230400, 460800, 500000, 576000,
+                 921600, 1000000)
+
+    def __init__(self, *args, **kwargs):
+        self._hid_handle = None
+        self._read_buffer = None
+        self._thread = None
+        super(Serial, self).__init__(*args, **kwargs)
+
+    def open(self):
+        if self._port is None:
+            raise SerialException("Port must be configured before it can be used.")
+        if self.is_open:
+            raise SerialException("Port is already open.")
+
+        self._read_buffer = Queue.Queue()
+
+        self._hid_handle = hid.device()
+        try:
+            portpath = self.from_url(self.portstr)
+            self._hid_handle.open_path(portpath)
+        except OSError as msg:
+            raise SerialException(msg.errno, "could not open port {}: {}".format(self._port, msg))
+
+        try:
+            self._reconfigure_port()
+        except:
+            try:
+                self._hid_handle.close()
+            except:
+                pass
+            self._hid_handle = None
+            raise
+        else:
+            self.is_open = True
+            self._thread = threading.Thread(target=self._hid_read_loop)
+            self._thread.setDaemon(True)
+            self._thread.setName('pySerial CP2110 reader thread for {}'.format(self._port))
+            self._thread.start()
+
+    def from_url(self, url):
+        parts = urlparse.urlsplit(url)
+        if parts.scheme != "cp2110":
+            raise SerialException(
+                'expected a string in the forms '
+                '"cp2110:///dev/hidraw9" or "cp2110://0001:0023:00": '
+                'not starting with cp2110:// {{!r}}'.format(parts.scheme))
+        if parts.netloc:  # cp2100://BUS:DEVICE:ENDPOINT, for libusb
+            return parts.netloc.encode('utf-8')
+        return parts.path.encode('utf-8')
+
+    def close(self):
+        self.is_open = False
+        if self._thread:
+            self._thread.join(1)  # read timeout is 0.1
+            self._thread = None
+        self._hid_handle.close()
+        self._hid_handle = None
+
+    def _reconfigure_port(self):
+        parity_value = None
+        if self._parity == serial.PARITY_NONE:
+            parity_value = 0x00
+        elif self._parity == serial.PARITY_ODD:
+            parity_value = 0x01
+        elif self._parity == serial.PARITY_EVEN:
+            parity_value = 0x02
+        elif self._parity == serial.PARITY_MARK:
+            parity_value = 0x03
+        elif self._parity == serial.PARITY_SPACE:
+            parity_value = 0x04
+        else:
+            raise ValueError('Invalid parity: {!r}'.format(self._parity))
+
+        if self.rtscts:
+            flow_control_value = 0x01
+        else:
+            flow_control_value = 0x00
+
+        data_bits_value = None
+        if self._bytesize == 5:
+            data_bits_value = 0x00
+        elif self._bytesize == 6:
+            data_bits_value = 0x01
+        elif self._bytesize == 7:
+            data_bits_value = 0x02
+        elif self._bytesize == 8:
+            data_bits_value = 0x03
+        else:
+            raise ValueError('Invalid char len: {!r}'.format(self._bytesize))
+
+        stop_bits_value = None
+        if self._stopbits == serial.STOPBITS_ONE:
+            stop_bits_value = 0x00
+        elif self._stopbits == serial.STOPBITS_ONE_POINT_FIVE:
+            stop_bits_value = 0x01
+        elif self._stopbits == serial.STOPBITS_TWO:
+            stop_bits_value = 0x01
+        else:
+            raise ValueError('Invalid stop bit specification: {!r}'.format(self._stopbits))
+
+        configuration_report = struct.pack(
+            '>BLBBBB',
+            _REPORT_GETSET_UART_CONFIG,
+            self._baudrate,
+            parity_value,
+            flow_control_value,
+            data_bits_value,
+            stop_bits_value)
+
+        self._hid_handle.send_feature_report(configuration_report)
+
+        self._hid_handle.send_feature_report(
+            bytes((_REPORT_GETSET_UART_ENABLE, _ENABLE_UART)))
+        self._update_break_state()
+
+    @property
+    def in_waiting(self):
+        return self._read_buffer.qsize()
+
+    def reset_input_buffer(self):
+        if not self.is_open:
+            raise portNotOpenError
+        self._hid_handle.send_feature_report(
+            bytes((_REPORT_SET_PURGE_FIFOS, _PURGE_RX_FIFO)))
+        # empty read buffer
+        while self._read_buffer.qsize():
+            self._read_buffer.get(False)
+
+    def reset_output_buffer(self):
+        if not self.is_open:
+            raise portNotOpenError
+        self._hid_handle.send_feature_report(
+            bytes((_REPORT_SET_PURGE_FIFOS, _PURGE_TX_FIFO)))
+
+    def _update_break_state(self):
+        if not self._hid_handle:
+            raise portNotOpenError
+
+        if self._break_state:
+            self._hid_handle.send_feature_report(
+                bytes((_REPORT_SET_TRANSMIT_LINE_BREAK, 0)))
+        else:
+            # Note that while AN434 states "There are no data bytes in
+            # the payload other than the Report ID", either hidapi or
+            # Linux does not seem to send the report otherwise.
+            self._hid_handle.send_feature_report(
+                bytes((_REPORT_SET_STOP_LINE_BREAK, 0)))
+
+    def read(self, size=1):
+        if not self.is_open:
+            raise portNotOpenError
+
+        data = bytearray()
+        try:
+            timeout = Timeout(self._timeout)
+            while len(data) < size:
+                if self._thread is None:
+                    raise SerialException('connection failed (reader thread died)')
+                buf = self._read_buffer.get(True, timeout.time_left())
+                if buf is None:
+                    return bytes(data)
+                data += buf
+                if timeout.expired():
+                    break
+        except Queue.Empty:  # -> timeout
+            pass
+        return bytes(data)
+
+    def write(self, data):
+        if not self.is_open:
+            raise portNotOpenError
+        data = to_bytes(data)
+        tx_len = len(data)
+        while tx_len > 0:
+            to_be_sent = min(tx_len, 0x3F)
+            report = to_bytes([to_be_sent]) + data[:to_be_sent]
+            self._hid_handle.write(report)
+
+            data = data[to_be_sent:]
+            tx_len = len(data)
+
+    def _hid_read_loop(self):
+        try:
+            while self.is_open:
+                data = self._hid_handle.read(64, timeout_ms=100)
+                if not data:
+                    continue
+                data_len = data.pop(0)
+                assert data_len == len(data)
+                self._read_buffer.put(bytearray(data))
+        finally:
+            self._thread = None
diff --git a/setup.py b/setup.py
index 6e8b586..ea53643 100644
--- a/setup.py
+++ b/setup.py
@@ -97,4 +97,7 @@
     ],
     platforms='any',
     scripts=['serial/tools/miniterm.py'],
+    extras_require = {
+        'cp2110': ['hidapi'],
+    },
 )