Farrell and Smith to start for England in quarter-final against Fiji
Farrell replaces George Ford at fly-half while Smith, a specialist No. 10, comes in at full-back in place of Freddie Steward.
Ford, who won two man-of-the-match awards for his impressive performances in pool wins over Argentina and Japan, is named on the bench while Steward drops out of the match-day 23.
In other changes made by coach Steve Borthwick, Elliot Daly comes in on the left wing with Jonny May switching to the right flank.
Joe Marchant reverts to outside centre and Manu Tuilagi to inside centre.
"The knockout stages of any Rugby World Cup are always full of excitement and keen anticipation for our supporters both at home and here in France. This will be no different," said Borthwick.
"The players cannot wait for this Sunday's quarter-final against Fiji."
Borthwick added: "Everyone knows just what an unpredictably dangerous opposition Fiji can be.
"However, we have shown in the group stages how we can win games, and we will be calling on that experience and determination to ensure we carry on our journey.
"We are very much looking forward to returning to the special atmosphere of the Stade de Marseille, where we started our campaign back in September with a win against Argentina."
England (15-1)
Marcus Smith; Jonny May, Joe Marchant, Manu Tuilagi, Elliot Daly; Owen Farrell (capt), Alex Mitchell; Ben Earl, Tom Curry, Courtney Lawes; Ollie Chessum, Maro Itoje; Dan Cole, Jamie George, Ellis Genge
Replacements: Theo Dan, Joe Marler, Kyle Sinckler, George Martin, Billy Vunipola, Danny Care, George Ford, Ollie Lawrence
Coach: Steve Borthwick