LSU's first College Football Playoff appearance will come as the No. 1 seed.
The selection committee announced the Tigers (13-0) as the country's top-ranked team Sunday entering a pair of national semifinals Dec. 28.
LSU will face No. 4 Oklahoma (12-1) at 3 p.m. in the Chick-fil-A Peach Bowl in the Atlanta.
"(The ranking) didn't matter to us," coach Ed Orgeron said. "Anytime, anywhere, anybody, we're ready to play. So we're gonna be playing Oklahoma, a great football team. Wherever they tell us to show up, we're gonna show up, and we're gonna be ready."
No. 2 Ohio State (13-0) and No. 3 Clemson (13-0), the defending national champion, will play at 7 p.m. the same day in the PlayStation Fiesta Bowl in the Phoenix area.
"We looked at schedule strengths," said committee chairman Rob Mullens, the athletic director at Oregon. "And you've got LSU 4-0 against teams in the top 13 and Ohio State 5-0 against teams in the top 21, it was really close. We've spent the entire ranking season, the six weeks, of just one going above the other, going above the other, just by a tick.
"And the last couple weeks we saw an LSU defense healthy, playing better, continued quality play out of Joe Burrow at the quarterback position. And this week, we just felt that LSU deserved the No. 1 see going into the Playoff."
The SEC champion Tigers haven't met the Sooners since Jan. 4, 2004, in New Orleans, where then-coach Nick Saban, senior quarterback Matt Mauck and company won the program's first national title in 46 years.
Oklahoma needed some help this weekend to set up this month's reunion.
LSU's emphatic 37-10 victory in Saturday's SEC Championship not only propelled itself back to No. 1, but knocked Georgia (11-2) from its position in the top four.
No. 5 Utah (11-2) also faltered Friday in the Pac-12 title game Friday.
And the Sooners and former Alabama quarterback Jalen Hurts rebounded from a deficit to Baylor (11-2) in Saturday's Big 12 championship to win, 30-23, in overtime.
"That conference championship and second win against Baylor moved them into the No. 4 spot," Mullens said. "We did spend some time talking about Oklahoma and Georgia, but in the end it was a solid Oklahoma selection for the No. 4 spot."
So the nation's top two FBS offenses — each averaging more than 560 yards per contest — will meet in Atlanta.
The two semifinal winners will then compete for a national championship Jan. 13, 2020, in New Orleans.
"I had my first home visit this morning, recruiting," Orgeron said. "I have two other home visits today. I'll be in about 18 homes this week, so we're gonna recruit a great class for this great university.
"We're gonna give the players a week off, and we''ll start preparation next Monday — Monday, Tuesday, Wednesday and Thursday — and we'll let 'em go home for Christmas and come back and practice here a couple days here and head over."