Grazer, director Ron Howard's longtime collaborator, will share producing duties with Don Mischer for the Feb. 26 Oscars ceremony.
Ratner, with whom Grazer worked on the big-screen comedy "Tower Heist," this week bowed out of producing the Academy Awards telecast after he created a media firestorm by publicly using a slang word for gays.
Eddie Murphy, one of the stars of "Tower Heist," was to serve as host of the Oscars, but quit Wednesday in the wake of Ratner's resignation. His replacement has not yet been announced.
"Brian Grazer is a renowned filmmaker who over the past 25 years has produced a diverse and extraordinary body of work," Academy of Motion Picture Arts and Sciences President Tom Sherak said in a statement. "He will certainly bring his tremendous talent, creativity and relationships to the Oscars."
"I am thrilled to welcome Brian Grazer as my partner and that we will be collaborating to produce an outstanding show," added Mischer.
"It's very gratifying to be part of a show that honors excellence in the medium to which I have devoted so much of my career," said Grazer. "Don is a legend, and I am excited to work with him."
Grazer won a Best Picture Oscar in 2001 for "A Beautiful Mind." In 1984, he was nominated in the writing category for "Splash," and he received Best Picture nominations for "Apollo 13" in 1995 and "Frost/Nixon" in 2008.