Lucy Amelia Nancy Moss (born 13 January 1994) is a British musical theatre composer, lyricist, playwright, writer, and director best known for co-creating the hit musical Six with Toby Marlow. As director of most Six productions, Moss became the youngest ever female director of a Broadway musical at 26.

For its West End run, Six was voted Best New Musical of the Decade by readers of WhatsOnStage and received five Olivier Award nominations. Nominated for a Tony Award for Best Direction of a Musical with Jamie Armitage, Moss alongside Marlow won the Tony Award for Best Original Score in 2022.

Before theatres reopened in 2021, Moss directed the virtual benefit performance of Ratatouille: The TikTok Musical. In 2022, Moss directed a new production of Legally Blonde: The Musical at Regent's Park Open Air Theatre in London.