The No. 1 Tigers will face the No. 4 Crimson Tide in the Allstate Sugar Bowl, and the No. 2 Sooners will play the No. 3 Bulldogs in the Rose Bowl Game presented by Northwestern Mutual on Jan. 1, as announced Sunday by the CFP selection committee.
The rest of the New Year's Six bowls fell this way: USC (11-2) vs. Ohio State (11-2) in the Cotton Bowl on Dec. 29; Washington (10-2) vs. Penn State (10-2) in the Fiesta Bowl on Dec. 30; Miami (11-1) vs. Wisconsin (12-1) in the Orange Bowl on Dec. 30; and UCF (12-0) vs. Auburn (10-3) in the Peach Bowl on Jan. 1.
Georgia is seeking its first national title since 1980, the longest active drought among teams in the CFP. Clemson won in 2016, Alabama won in 2015 and Oklahoma won in 2000.
Alabama opened as a 1-point favorite over Clemson, and Oklahoma opened as a 3-point favorite over Georgia at the Westgate Las Vegas SuperBook.
The semifinal winners will play for the national title on Jan. 8 in Atlanta.
It's the third straight season that Alabama and Clemson will meet in the playoffs, though this time in the semifinals. The Tide beat the Tigers in a classic national championship game in Glendale, Arizona, two seasons ago. The teams played another thriller last season, and Clemson took the title in Tampa, Florida.
It's just the second time that two teams will have met in a bowl game in three straight years. USC and Ohio State played in the Rose Bowl in three consecutive years from 1972 to 1974.
Alabama (11-1) made the cut despite being idle Saturday and not winning the SEC title. Its lone loss was a 26-14 setback to Auburn in the Iron Bowl on Nov. 25.
CFP committee chairman Kirby Hocutt said the 31-point loss to Iowa weighed Ohio State down, and the Buckeyes were not close enough to the Tide for the Big Ten championship result to matter.
"As we saw Alabama play week in and week in out, the selection committee believed Alabama was the better football team,'' Hocutt said. "When we looked at Ohio State, when you looked at their résumé, it was impressive, but it wasn't enough for the selection committee to place them in above Alabama."
Ohio State coach Urban Meyer said he was not surprised that the Iowa loss cost the Buckeyes.
"I was kind of hoping we had those good wins. Three against the top 16 teams in America,'' Meyer told ESPN. "But I get it.''
He added: "The bottom line is we had a tough road loss.''
By choosing Alabama over Ohio State for the No. 4 spot, the selection committee had to deem the Tide "unequivocally" better, which allows it to disregard the tiebreaker criteria. It is the same scenario that allowed the Buckeyes to get in last year without winning their division and in spite of a head-to-head loss to Penn State.
Alabama is the only team to have appeared in every playoffs since they began in 2014.
Ohio State finished No. 5 and Wisconsin No. 6.
After a 38-3 blowout win over Miami, defending national champion Clemson (12-1) has now won three straight ACC titles and clinched the No. 1 spot in the playoff rankings for the second time in three years.
Oklahoma (12-1) overcame a stunning loss to Iowa State in October to win its third straight Big 12 title with a commanding 41-17 win over TCU.
Georgia (12-1) thrashed Auburn 28-7 in the SEC championship game, avenging its only loss of the season -- an ugly 40-17 defeat at Auburn three weeks ago in which it was thoroughly dominated on both sides of the ball.
Georgia and Oklahoma have never played. The Bulldogs have surged in their second season under coach Kirby Smart. After winning eight games last season, Georgia won the SEC for the first time since 2005.
Oklahoma is in the playoff for the second time and will likely bring the Heisman Trophy winner. Quarterback Baker Mayfield is the favorite to win the award next weekend. If so, Mayfield will be the third player to go from winning the Heisman on to the playoff, joining Oregon's Marcus Mariota in 2014 and Alabama's Derrick Henry in 2015.
Oklahoma's Lincoln Riley is the first coach to reach the College Football Playoff in his first season as an FBS head coach. Only two coaches in the poll era (since 1936) have won a national title in their first season coaching at the major-college level: Larry Coker at Miami in 2001 and Bennie Oosterbaan at Michigan in 1948.
The four coaches received significant bonuses for leading their teams to the playoff. Georgia's Kirby Smart receives $500,000, Clemson's Dabo Swinney and Alabama's Nick Saban each earn $200,000, while Oklahoma's Riley gets $75,000.
ESPN's Darren Rovell, ESPN Stats & Information and The Associated Press contributed to this report.