If you're talking about My Fair Lady, Eliza was acted by Audrey Hepburn and her singer was Marni Nixon, Henry Higgins was both acted and sung by Rex Harrison, Eliza's father Mr Doolittle was both acted and sung by Stanley Holloway. The only characters I don't know are Henry Higgin's mother, Freddy Einsfordhill Eliza's potential lover, and Colonel Pickering.
Many actors and actresses have played the lead roles.
The most famous are perhaps Audrey Hepburn as Eliza Dolittle and Rex Harrison as Professor Higgins in the 1964 film
The cast of Fair Rent - 1947 includes: Norrie Williamson as Fraser
The cast of My Fair Dolly - 1994 includes: Leo Rozenstraten as Horloger
The cast of A Dream of Fair Women - 1920 includes: Russell Ball
The cast of Fair Week - 1922 includes: James Parrott Jobyna Ralston
The cast of Fair Dinkum Manjit - 2006 includes: Manjit Boparai as himself
The cast of Fair But False - 1920 includes: Bobby Vernon
The cast of The Fair Employer - 2012 includes: John Grooters
The cast of A Fair to Remember - 2008 includes: Barry Corbin
The cast of Fair Bits - 2005 includes: Taj Burrow
The cast of Fancy Fair - 2011 includes: Dominique Bayens
The cast of The Story of the Fair - 2009 includes: Dave Dugan as Narrator
The cast of My Fair Clair - 2013 includes: Herve Achi as Narrator
The cast of Fair Rent - 1947 includes: Norrie Williamson as Fraser
The cast of My Fair Dolly - 1994 includes: Leo Rozenstraten as Horloger
The cast of A Dream of Fair Women - 1920 includes: Russell Ball
The cast of The Fair Maid of Perth - 1926 includes: Louise Maurel
The cast of All Is Fair - 1912 includes: William Clifford as Dick Cartwright