Center Hroniss Grasu also will return to Oregon for the 2014 season.
Mariota, a redshirt sophomore from Honolulu, and Grasu, a redshirt junior from Los Angeles, announced their intentions a day after earning all-Pac-12 accolades from the conference's head coaches for the second straight year.
Mariota is rated as the No. 3 overall prospect by NFLDraftScout.com for players potentially eligible for the 2014 draft and the No. 2 quarterback behind Louisville's Teddy Bridgewater. Mariota is the No. 1 overall prospect, just ahead of Texas A&M quarterback Johnny Manziel, for their draft class of 2016.
"It is an honor to be a student at the University of Oregon and to have the opportunity to represent our institution on the football field alongside my teammates," Mariota said. "I look forward to earning my degree next year and to the rest of my career at this great University."
Mariota, who has claimed a share of Oregon's Most Outstanding Player honors in each of his first two seasons, completed 227 of 360 passes (63.1 percent) for 3,412 yards and 30 touchdowns as a sophomore, with his 3,994 yards of total offense setting a single-season school record.
Mariota, the 2012 Pac-12 Offensive Freshman of the Year, has started all 25 games for the Ducks in his two seasons and is currently the conference's career leader in pass efficiency rating at 165.67. He is the only quarterback from a BCS auto-qualification conference team to pass for at least 30 touchdowns the past two years and his current streak of 25 straight games with at least one touchdown pass is the third-longest in the nation.
Grasu, a three-year starter at center, has anchored an Oregon offensive line that played a pivotal role in the Ducks' winning back-to-back BCS bowl games the past two seasons and achieved a 10-2 regular season this year. The 2012 third-team all-America was a candidate for the Lombardi Award, Outland Trophy and Rimington Trophy this season.
"The University of Oregon is a special place and I'm extremely happy to be returning for my senior year," Grasu said. "To be a student-athlete in this community is an honor and an experience I'll continue to cherish with my teammates."