Janet Leach is an English social worker, known for the role she played as an appropriate adult in the questioning of Fred West, one of the two perpetrators of the Gloucester serial murders. For these murders, he and his wife Rose West, against whom Leach testified at trial, became notorious.

The murders—first committed by Fred before he met Rose and then by the two of them as co-conspirators—included the kidnapping, rape, torture, and murder of various young women, including their own children and stepchildren. Fred killed himself in his cell while on remand on New Year's Day 1995. Rose was convicted and became one of four women in Britain to be given a whole life tariff, the others being Myra Hindley, Joanna Dennehy and Lucy Letby.