William Thomas Missingham (15 May 1868 – 1 February 1933) was an Australian politician.
He was born at Jamberoo to farmer David Missingham and Priscilla, née Noble.
Educated at Jamberoo and Kiama, he moved to the Richmond River area in 1890 to manage the Pearce Creek butter factory and, in 1898, became a dairy farmer.
On 25 November 1891, he married Margaret Elizabeth Dorrough, with whom he had four children.
In 1922, he was elected to the New South Wales Legislative Assembly as a Progressive member for Byron; he was the party's deputy leader from 1925 to 1932 (it had become the Country Party in 1927).