The US beer giants have sealed a three-year deal understood to be worth around £8million a year.
Parent company Anheuser-Busch InBev enjoy tie-ins with the NFL, Olympics, Major League baseball and the From Back Page World Cup - and the new sponsors plan to promote the competition globally.
E.ON stepped down as sponsors this year after five seasons.
An FA source said: "It's a great coup to get Budweiser as our sponsor.
"Many doubted we could attract a big name but this shows how attractive the competition still is.
"Regardless of what people say about the Champions League and Premier League, the FA Cup remains the world's greatest club competition."
FA chiefs came under fire last month when the Cup final was held on the same day as a full programme of Premier League fixtures, which saw Manchester United seal the title at Blackburn.
United were celebrating their triumph live on TV, with the FA Cup final between Manchester City and Stoke already under way at Wembley.
And FA chairman David Bernstein has already admitted the same scenario is likely to happen again this coming season.