Lyndy Brill (also known as Lindy Brill, born 30 July 1963) is a former actress and singer. She is best known for playing Cathy Hargreaves in the BBC school drama, Grange Hill (1979-82), and also appeared in an episode of The Sweeney (Nightmare) in 1978. She also appeared on Top of the Pops in 1978 as one of the St Winifred's School Choir backing singers on Brian and Michael's number 1 hit "Matchstalk Men and Matchstalk Cats and Dogs".

Brill continued to act after leaving Grange Hill, appearing in the West End and in the BBC miniseries Alexa and Claire in 1982, but she decided to end her acting career when she turned 30. She then worked in sales support for an educational book publisher.