Ann Mallalieu, Baroness Mallalieu QC (born 27 November 1945) is a British lawyer, Labour Party politician and president of the Countryside Alliance.
Lady Mallalieu comes from a distinguished political family. Her grandfather, Frederick Mallalieu, had been Liberal Member of Parliament for Colne Valley. He was succeeded in that seat by her uncle, Lance Mallalieu, later Labour MP for Brigg. Her father, Joseph Percival William Mallalieu (known as William), was Labour MP for Huddersfield East. She was educated at Newnham College, Cambridge, where she was the first female president of the Cambridge Union Society.
Mallalieu fought Hitchin at both the February and October 1974 elections, but was defeated by the Conservative Ian Stewart on both occasions.
On 19 June 1991, Mallalieu was made a life peer as Baroness Mallalieu, of Studdridge in the County of Buckinghamshire. She was married to, but later divorced from, Sir Timothy Cassel, Bt, QC. They have two adult daughters.