Joseph Slater, Baron Slater, BEM (13 June 1904 – 21 April 1977) was a Labour Party politician in the United Kingdom.
He was elected as Member of Parliament (MP) for Sedgefield in County Durham at the 1950 general election, following the retirement of John Leslie. Slater held the seat until he retired from the House of Commons at the 1970 general election. In Harold Wilson's Labour Government 1964–1970, he served as Assistant Postmaster-General from 1964 to 1969, serving under four Postmasters-General: Tony Benn, Edward Short, Roy Mason and John Stonehouse.
On 8 July 1970 he was created a life peer as Baron Slater, of Ferryhill in County Durham.