William Henry Lambert (24 March 1881 – 6 September 1928) was an Australian politician and unionist, serving for one term as Lord Mayor of Sydney in 1921.

He used his casting vote to support Labor policy, and was noted for preferring the Australian flag to the Union Jack.

He kept a fairly low profile in Parliament, but became intimately involved in faction politics.

His political fortunes declined after Jack Lang became leader of the New South Wales Labor Party.

Lambert told the Daily Telegraph Pictorial that he had been offered £8000 in 1925 to resign his seat in favour of Ted Theodore.