Penelope J. Leach (born Penelope Jane Balchin, 19 November 1937 Hampstead, London) is a British psychologist who writes extensively on parenting issues from a child development perspective.
Leach is best known for her book Your Baby and Child: From Birth to Age Five, published in 1977, which has sold over two million copies to date. Leach notes in the introduction to that book: "Whatever you are doing, however you are coping, if you listen to your child and to your own feelings, there will be something you can actually do to put things right or make the best of those that are wrong."
She is the daughter of Nigel Balchin, the novelist and screenwriter. She graduated from Newnham College, Cambridge with honours in 1959. After Cambridge, she attended the London School of Economics, where she received her Ph.D. in psychology and lectured on child development. Her research positions have included a year in the Home Office Research Unit studying juvenile crime and six years at the Medical Research Centre Developmental Research Unit. Leach is a fellow of the British Psychological Society and was previously President of the National Childminding Association.