The Miss Congeniality star's career is at an all-time high despite her personal woes - she's landed at number one as the highest-earning actress over the last year, taking in $56 million (£37.3 million) between June 2009 and June 2010.
Forbes editors looked at income from film roles in addition to money that stars might have earned from perfume deals, clothing lines and ad campaigns.
Securing Bullock's top spot were her roles in The Proposal and The Blind Side - which won the star her first Oscar last year (09), for best leading actress.
Witherspoon and Diaz followed, each earning about $32 million (£21.3 million).
The pair is followed by Jennifer Aniston in fourth place with $27 million (£18 million), and Sex & the City star Sarah Jessica Parker, who ranks fifth on the list with $25 million (£16.7 million).
Bullock's home life was rocked earlier this year (10), when news of her ex-husband Jesse James' alleged affairs hit headlines. The ex-couple's divorce was finalised in June (10), shortly after Bullock revealed she and James had adopted a baby boy.