Betsy Reilly Lewin (born May 12, 1937) is an American illustrator from Clearfield, Pennsylvania. She studied illustration at Pratt Institute. After graduation, she began designing greeting cards.

She started writing and illustrating stories for children's magazines and eventually children's books. Betsy Lewin is married to children's book illustrator Ted Lewin and has co-written and illustrated several books about their travels to remote places, including Uganda in Gorilla Walk and Mongolia in Horse Song, as well as How to Babysit a Leopard: and Other True Stories from Our Travels Across Six Continents published by Roaring Brook Press in 2015.

She is arguably best known for the Caldecott Honor Book Click Clack Moo: Cows that Type.