Janet Ahlberg (1944-1994) was a British children's book illustrator, and the co-creator, together with her husband Allan Ahlberg, of the best-selling Jolly Postman series. Born as Janet Hall in Yorkshire in 1944, she studied at Sunderland Technical College, where she met Ahlberg. The two married in 1969, and began to work together, publishing their first co-venture - The Old Joke Book - in 1976. She won the 1978 Kate Greenaway Medal from the British Library Association - an award recognizing the year's best children's book illustration by a British subject - for Each Peach Pear Plum.

Janet Ahlberg died of breast cancer in 1994, at the age of fifty, having produced many beloved and bestselling books. Her daughter with Allan Ahlberg - Jessica Ahlberg - is also a children's book creator.