Marsha Lisa Thomason (born 19 January 1976) is an English television and film actress who is best known for playing Nessa Holt in the first two seasons of the NBC series Las Vegas, Naomi Dorrit on the ABC series Lost, and FBI agent Diana Berrigan on the USA Network series White Collar.
Thomason was born in Moston, Greater Manchester, the daughter of Phyllis (née McCrae), a Jamaican electronics company employee, and Peter Thomason, who worked in politics. She attended Holy Trinity Primary School in Harpurhey and North Manchester High School for Girls in Moston, before attending Oldham Sixth Form College to study for A levels in media studies, theatre studies, and performing arts. Thomason attended the Manchester Metropolitan University, receiving a bachelor of arts degree in English. From the age of 13, Thomason attended Oldham Theatre Workshop, where she participated in youth theatre productions.