Mary Anne Lamb (December 3, 1764–May 20, 1847), was an English writer, the sister and collaborator of Charles Lamb.

In 1796, Mary, who had suffered a breakdown from the strain of caring for her family, killed her mother with a kitchen knife, and from then on had to be kept under constant supervision. When their senile father died, her younger brother became her official guardian. In 1807, she collaborated with him on a children's book, Tales from Shakespeare, and they produced other popular works for children in later years. Mary continued to suffer bouts of mental illness throughout her life. After Charles' death in 1834, she was cared for at times by a family and at others in an asylum.

On her death, she was buried next to her brother.