Title: Clemson Tigers
Content:  Clemson has three national championships in football, the most recent coming in 2018 with a victory over Alabama 44-16 in the 2019 College Football Playoff National Championship. Clemson has appeared in the last six playoffs and won two national championships during those visits. The Tigers also possess the most Atlantic Coast Conference championships with 20, including winning the last six. It has also won greater than 60% of its games, placing it in the top 25 on the all-time winning percentage list. Clemson also won two Southern Conference titles before joining the ACC. The 1981 squad, led by Head Coach Danny Ford, became the first athletic team in school history to win a national championship. Clemson defeated Nebraska 22&ndash;15 in the Orange Bowl 
Title: Game of the Century (college football)
Content:  in the CFP to No. 5, and No. 2 to No. 4 in the AP and Coaches Polls. Alabama's subsequent loss in the Iron Bowl later that year would drop the Crimson Tide out of contention for the College Football Playoff for the first time in the history of the playoffs. LSU would go on to defeat the defending National Champion Clemson Tigers in the CFP National Championship game to cap off a perfect 15–0 season and be crowned National Champions for the first time in the CFP era. It was LSU's first time playing for the National Championship since the loss to Alabama in the 2012 BCS National Championship Game, and their first title since the 2007 season.
Title: 2020 College Football Playoff National Championship
Content:  Clemson defeated Virginia in the ACC Championship Game on December 7, and received a bid to the Fiesta Bowl with the release of final CFP rankings on December 8. On December 28, the Tigers defeated Ohio State in the CFP semifinal Fiesta Bowl, 29–23. Clemson also entered the championship game with a 14–0 record (8–0 in conference). The Tigers' most recent loss had been to Alabama in the CFP semifinal Sugar Bowl on January 1, 2018; their 29 consecutive victories following that loss constituted one of the longest NCAA Division I football winning streaks. Including national championship contests, this was Clemson's ninth overall CFP game; they had a 6–2 record in prior CFP games, and were the defending champions, having defeated Alabama in the 2019 CFP National Championship.
Title: Clemson Tigers football
Content:  since 1991, defeating Virginia Tech 38–10 in the Championship Game. However, in the 2012 Orange Bowl, their first major-bowl appearance since the 1981 national championship season, No. 15 Clemson was routed by No. 23 West Virginia 70–33, giving up an all-time record number of points scored in a quarter (35), half (49) and game (70) in the 109-year history of bowl games. On December 31, 2012, Clemson achieved its first 11-win season since the national championship year with a last-second upset win over the No. 8 LSU Tigers in the Chick-fil-A Bowl. Clemson trailed 24–13 in the fourth quarter, but rallied 
Title: 2016 Clemson Tigers football team
Content:  By winning the Fiesta Bowl, Clemson advanced to the 2017 College Football Playoff National Championship to face the winner of the Peach Bowl, top-seeded Alabama (14–0). Clemson had lost to Alabama in the previous year's national championship, and this marked the first time since the inception of college football national title games in the 1990s of a rematch played between two schools. Alabama was considered a 6.5-point favorite to repeat as champions. Clemson won in dramatic fashion, 35–31, to secure their first national title since 1981. Alabama was the first to score, with a 25-yard touchdown by Bo Scarbrough. They extended their lead to 14 with a 37-yard touchdown run early in the second quarter, 
Title: 2019 College Football Playoff National Championship
Content:  at Alabama's 48-yard-line. Alabama began their fourth second-half drive with just over eleven minutes on the clock and Jalen Hurts at quarterback; it ended in a three-and-out, and Mike Bernier's punt was downed at the Clemson one-yard-line. After draining more than seven minutes on the clock and with the ball on Alabama's 17-yard-line, the majority of Clemson's offensive starters were removed from the game and Chase Brice was put in at quarterback. Clemson used up the remaining two minutes off the clock and took a knee on the final play ending the longest drive (10:02) in Clemson history and winning the National Championship, their second title in three years.
Title: History of Clemson Tigers football
Content:  the Championship Game. No. 15 Clemson would go on to lose to the No. 23 West Virginia Mountaineers in the 2012 Orange Bowl 70–33, giving up an all-time record number of points scored in a quarter (35), half (49) and game (70) in the 109-year history of bowl games. On December 31, 2012, Clemson achieved its first 11-win season since the national championship year with a last-second upset win over the No. 8 LSU Tigers in the Chick-fil-A Bowl. Clemson trailed 24–13 in the fourth quarter, but rallied back with a game-winning drive that saw a 4th and 16 
Title: Clemson Tigers
Content: Men's (7) ; Golf (1): 2003 ; Soccer (3): 1984, 1987, 2021 ; Football (3): 1981, 2016, 2018 see also: ; ACC NCAA team championships ; [[List of NCAA schools with the most NCAA Division I championships#NCAA Division I Team Championships|List of NCAA schools with the most NCAA Division I championships]] Clemson University has four team national championships awarded by the NCAA. Clemson has also won three Division I Football National Championships, in 1981, 2016, and 2018. These titles were awarded by polling services in 1981, and by the College Football Playoff system in 2016 and 2018.  
Title: 2019 College Football Playoff National Championship
Content:  Alabama held a 14–4 series lead over Clemson in prior meetings between the two teams. They had met in the postseason in each of the prior three seasons: the 2016 College Football Playoff National Championship, won by Alabama (45–40); the 2017 College Football Playoff National Championship, won by Clemson (35–31); and the 2018 Sugar Bowl playoff semifinal game, won by Alabama (24–6). This was the first time under the College Football Playoff format (initiated in 2014) that an undefeated team won the championship, as both teams came into the game 14–0. The most recent prior matchup of undefeated teams in a championship game had been the 2011 BCS National Championship Game, which saw 13–0 Auburn defeat 12–0 Oregon. The most recent undefeated winner of a national championship game had been Florida State, who won the 2014 BCS National Championship Game and finished their season with a 14–0 record.
Title: History of Clemson Tigers football
Content:  to rank No. 2 in the final CFP rankings. As expected from last season's returning starters, quarterback Deshaun Watson anchored an explosive offense that averaged 503 yards per game. The defense reloaded behind a standout defensive line and limited opponents to just 18.4 points a game. Clemson finished with a regular season record of 12–1, which culminated with a 56–7 win at home over arch-rival South Carolina, Swinney's largest margin of victory over the Gamecocks during his career. Clemson won the ACC championship and secured its second trip to the CFP National Championship with a 31–0 shutout of semi-finalist 

Question: when was the last time clemson won the national championship?
Answer: 2016.