Butler got downhill and hit a 17-foot two-point shot as time expired completing a remarkable 14-point second-half comeback for the Aztecs.
It was the first buzzer-beater during this NCAA tournament and only the fifth in the Final Four history.
Aztecs coach Brian Dutcher opted against calling a timeout when Nathan Mensah rebounded Johnell Davis' missed jumper with the Owls leading 71-70 with 10 seconds left, before Butler drove on and took responsibility with his buzzer-beater for the ages.
"I didn't really know how big it was," Butler said who was mobbed by teammates and coaches. "We're going to the national championship. That's not things many people do."
After trailing 40-33 at half-time, SDSU found its defensive grip to work its way back into the contest, with Matt Bradley scoring 21 points with six rebounds.
Alijah Martin top scored for FAU with 26 points including three triples along with seven rebounds.
The Aztecs will face UConn who accounted for the Miami Hurricanes 72-59 with forward Adama Sanogo outstanding with 21 points including two three-pointers and 10 rebounds.
UConn advanced to their fifth National Championship game, with the Huskies having not lost to a non-conference opponent this year and winning all five NCAA games by double digits.
Huskies guard Jordan Hawkins overcame illness to contribute 13 points, while Miami's Isaiah Wong scored a team-high 15 points on four-of-10 shooting with their offense blunted, going at 32.3 per cent from the field as a team.
With their seasons on the line, the two sides combined to shoot a dismal five-of-30 (16.6 per cent) from three-point range, but there were no such struggles for Aztecs junior guard Lamont Butler.
Butler posted a game-high 18 points on eight-of-11 shooting, nailing both of his three-point attempts, while only committing one turnover in his 30 minutes.
Seven-foot-one Creighton center Ryan Kalkbrenner continued his strong NCAA Tournament with a team-high 17 points (eight-of-17 shooting), six rebounds and two blocks.
It was not without controversy though, as after Bluejays senior transfer Baylor Scheierman tied the game with 32 seconds remaining, San Diego State's Darrion Trammell was fouled on the potential game-winning floater with 1.2 seconds on the clock.
Creighton's players and coaches were apoplectic at the call, which was borderline, and after Trammell missed the first free throw, he drained the second to secure the one-point victory.
They will face this year's most unlikely Final Four participants next, with Florida Atlantic waiting in the wings after having never won a single game in the NCAA Tournament prior to this season.
Meanwhile, the five-seed Miami Hurricanes also booked their ticket to the first Final Four in school history after an 88-81 triumph over two-seed Texas.
The Hurricanes were coming off their first ever Elite 8 appearance in 2022, and they have gone even further this time around thanks in large part to the spectacular showing from senior wing Jordan Miller.
Miller scored a game-high 27 points – his highest total since November 2020 – while shooting a perfect seven-of-seven from the field and 13-of-13 from the free throw line.
All five of Miami's starters scored at least 11 points each, and they did it in old-school fashion, shooting 59 per cent from the field while only attempting eight three-pointers as a team.
The Hurricanes will meet the Connecticut Huskies in the Final Four, who are the only team seeded fourth or lower in NCAA Tournament history to win four games in a row by double-digits.
The Spartans rode a 23-point performance from senior point guard Tyson Walker, while Joey Hauser – brother of Boston Celtics wing Sam Hauser – collected 14 points and 10 rebounds.
As well as pulling into a tie for the sixth-most Sweet 16 appearances in head coaching history, Izzo also claimed the record for the most ever NCAA Tournament wins as the lower seed, with this his 16th.
He is one more Sweet 16 trip away from tying Louisville legend Denny Crum for the fifth-most, with only North Carolina's Roy Williams (19), Syracuse's Jim Boeheim (20), Michael Jordan's North Carolina coach Dean Smith (21) and Duke's Mike Krzyzewski (26) having more.
The seven-seed Spartans will next face three-seed Kansas State after they won the battle of the Wildcats 75-69 against six-seed Kentucky.
Reigning National Player of the Year Oscar Tshiebwe was monstrous with 25 points and 18 rebounds, while projected first-round draft pick Cason Wallace impressed with 21 points (nine-of-11 shooting), nine rebounds, four assists and two steals.
But their performances were not enough to lift Kentucky to the victory, as diminutive five-foot-eight point guard Markquis Nowell dropped a game-high 27 points and nine assists to carry Kansas State through.
Following his massive 28-point, 13-rebound showing in his side's opening-round win, Connecticut Huskies center Adama Sonogo starred again with 24 points (11-of-16 shooting) and eight rebounds in a 70-55 win over the Saint Mary's Gaels.
After Marquette, the top seed to fall Sunday was the three-seed Baylor Bears. Despite 30 points from Baylor guard L.J. Cryer, the Creighton Bluejays received a game-winning 30 points from Ryan Nembhard in the 85-76 triumph.
Nembhard is the younger brother of Andrew, who has been a rookie standout for the Indiana Pacers this season.
Following their stunning upset of one-seed Purdue, where they became the second 16-seed to ever advance past the first round, the Fairleigh Dickinson Knights were sent packing 78-70 by the nine-seed Florida Atlantic Owls.
Three-seed Xavier were in control throughout their 84-73 win against Pittsburgh, five-seed Miami prevailed 85-69 over four-seed Indiana, and four-seed Gonzaga sent six-seed TCU home 84-81.
The Crimson Tide were well below their best in a sloppy performance with 14 turnovers, shooting three-of-27 from beyond the arc.
SDSU's Darrion Trammell scored 21 points as San Diego progressed to the Elite Eight for the first time.
Trammell led the way offensively for the Aztecs, while Nathan Mensah had eight rebounds and five blocks, while Lamont Butler had three steals, four rebounds and four assists.
For Alabama, top-five NBA Draft prospect Brandon Miller scored nine points with 11 rebounds but committed six turnovers and shot three-of-19 from the field, including one-of-10 from three-point range.
Crimson Tide guard Mark Sears scored 16 points with 10 rebounds but shot none-of-five from beyond the arc.
"Everybody is really disappointed in the loss," Alabama coach Nate Oats said. "It ended too soon."
Midwest regional top seed Houston were also eliminated in the Sweet 16 on Friday after losing 89-75 to Miami.
Hurricanes guard Nijel Pack led the way with 26 points including seven-of-10 three-pointers as Miami made 11 of their first 22 attempts from beyond the arc.
Miami will take on Midwest second seed Texas in the Elite Eight after the Longhorns won ___ over the Xavier Musketeers, with Tyrese Hunter scoring a team-high __ points with __-of-__ three-pointers.
South regional six seed Creighton defeated Princeton 86-75 to set up a Elite Eight meeting with SDSU, after Ryan Kalkbrenner and Baylor Scheierman scored 22 and 21 points respectively.
The Peacocks thrived off a home-court advantage at the Wells Fargo Center to become the first 15th seed to reach the Elite Eight, despite the late efforts of NBA lottery prospect Jaden Ivey.
Despite hitting on none of his opening five attempts from the perimeter, Ivey connected on an NBA-range triple with eight seconds left to bring Purdue within a point. Doug Edert calmly made his free-throws to ice the game, and put Saint Peter's on the brink of the Final Four.
They will face North Carolina who defeated UCLA 73-66, led by 30 points from Caleb Love.
Despite shooting 10-of-31 from the three-point line for the night, the six-time national champions overcame a three-point deficit to put up 45 points in the second half.
Elsewhere, Remy Martin scored a season-high 23 points as Kansas hung on for a 66-61 win over Providence, securing their passage to the Elite Eight.
The Jayhawks are the only first seed left in the tournament, after both Gonzaga and Arizona were defeated in the Sweet 16 on Thursday, and Baylor's title defence was ended in the second round.
Kansas will face the Miami Hurricanes, who progressed with their comfortable 70-56 win over Iowa State.
