Redgrave, 72, was honored for her charity work, as well as her performances on stage and screen, at a ceremony at the Dorchester Hotel, the BBC said.
Fiennes co-starred with Redgrave and her late daughter, Natasha Richardson, in the 2005 film "The White Countess." He is also a friend to the family, including Richardson's husband, actor Liam Neeson.
"If I think of a woman of truth, of loyalty, of integrity, of passion, of compassion, a woman with a great heart and a woman of all elements, I think of Vanessa Redgrave," the BBC quoted Fiennes as saying. "You might think I'm a bit in love, but I'm just a fan and a friend, and if I am it's because of a great friendship I shared with Natasha and through that great friendship I've got to know Vanessa. Natasha was imbued with so many of your fantastic qualities, as well as many of her own, and I feel blessed to have had that friendship, and, thus, through that friendship to have known Vanessa."
Richardson died at 45 last March of head injuries sustained in a skiing accident.