In the 1968 NCAA University Division football season, the system of "polls and bowls" changed. The Associated Press returned to its pre-1961 system of ranking the Top 20 rather than the Top 10, and voted on the national champion after the bowl games, rather than before. During the 20th century, the NCAA had no playoff for the major college football teams in the University Division, later known as Division I-A.

The NCAA Football Guide, however, did note an "unofficial national champion" based on the top ranked teams in the "wire service" (AP and UPI) polls. The "writers' poll" by Associated Press (AP) was the most popular, followed by the "coaches' poll" by United Press International) (UPI). In 1968, the UPI issued its final poll before the bowls, but the AP Trophy was withheld until the postseason was completed.

The AP poll in 1968 consisted of the votes of as many as 49 sportswriters, though not all of them voted in every poll. With a Top 20 for the first time since the 1960 season, there were more matchups between ranked teams. Those who cast votes would give their opinion of the ten best teams. Under a point system of 20 points for first place, 19 for second, etc., the "overall" ranking was determined. In 1969, there were four regular season games that matched "Top Five" teams.

• The 1967 punting rule requiring five linemen on the kicking team to remain at the line of scrimmage until the ball is punted was repealed.
• Eliminating the "flex shift" (offensive linemen raising up then dropping back down into position, used by Kansas and UCLA the previous season and later popularized by the Dallas Cowboys) by requiring an offensive player to hold his position when he gets "on or near the ground".
• The game clock will be stopped on all first downs to move the chains, then restarted again. This rule was modified in the 2023 season to only stop the clock for first downs inside of the final two minutes of each half.
• The "tackle-eligible" pass play was declared illegal by requiring five offensive lineman numbered 50–79 to be on the line of scrimmage and declaring none of them are eligible receivers.
• Prohibiting the receiver of a fair catch who does not catch the ball to then become a blocker.
• Limiting the legal clipping zone to a rectangular point three feet by four yards on either side of the ball.
• Defensive players who intercept a pass within five yards of the end zone and his momentum takes him into the end zone, the ball will be put in play at the spot of the interception if the defensive player does not attempt to advance the ball out of the end zone.
• Length of time-outs are shortened from 120 seconds to 90 seconds.

• Prior to the season, the Athletic Association of Western Universities officially renamed itself as the Pacific-8 Conference.

In the preseason poll released on September 9, the Purdue Boilermakers were picked No. 1, followed by the defending champion USC Trojans. Third was the Notre Dame Fighting Irish, followed by the Oklahoma Sooners and the Texas Longhorns. A second poll was taken on September 16 (with Texas and Oklahoma trading places), although most teams would not begin play until the 21st.

September 21 No. 1 Purdue beat Virginia 44–6, and No. 2 USC won 29–20 at No. 16 Minnesota. No. 3 Notre Dame beat No. 5 Oklahoma 45–21 at South Bend, while No. 4 Texas was tied 20–20 at home by No. 11 Houston. No. 6 Florida defeated Air Force 23–20 in Tampa, while No. 10 Penn State beat Navy 31–6. In a proud moment for football in Indiana, Purdue remained at No. 1, and Notre Dame rose to No. 2, days before the annual meeting between the two schools. The remainder of the top five was No. 3 USC, No. 4 Penn State, and No. 5 Florida.

September 28 No. 1 Purdue traveled to No. 2 Notre Dame and won, 37–22. No. 3 USC won 24–7 at Northwestern, No. 4 Penn State beat Kansas State 25–9, and No. 5 Florida won at Florida State 9–3. The next poll was No. 1 Purdue, No. 2 USC, No. 3 Penn State, No. 4 Florida, and No. 5 Notre Dame.

October 5 No. 1 Purdue won at Northwestern, 43–6, and No. 2 USC beat visiting No. 13 Miami (FL), 28–3. No. 3 Penn State won at West Virginia 31–20, No. 4 Florida beat Mississippi State 31–14, but fell from the Top Five, and No. 5 Notre Dame won at Iowa 51–28. With a 21–6 win over Oregon, No. 6 Ohio State moved up in the rankings. The next poll was No. 1 Purdue, No. 2 USC, No. 3 Penn State, No. 4 Ohio State, and No. 5 Notre Dame.

October 12 No. 1 Purdue lost 13–0 at No. 4 Ohio State, and No. 2 USC won 27–24 at No. 18 Stanford. No. 3 Penn State won at UCLA 21–6, No. 5 Notre Dame beat Northwestern 27–7, and No. 6 Kansas won 23–13 at No. 9 Nebraska. The next poll was No. 1 USC, No. 2 Ohio State, No. 3 Penn State, No. 4 Kansas, and No. 5 Purdue.

October 19 No. 1 USC beat Washington 14–7, and No. 2 Ohio State beat Northwestern 45–21. No. 3 Penn State was idle, No. 4 Kansas beat Oklahoma State 49–14, No. 5 Purdue edged Wake Forest 28–27, and No. 6 Notre Dame beat Illinois 58–8. The next poll was No. 1.USC, No. 2 Ohio State, No. 3 Kansas, No. 4 Penn State, and No. 5 Notre Dame.

October 26 No. 1 USC was idle, and No. 2 Ohio State won at Illinois 31–24. No. 3 Kansas won at Iowa State 46–25, No. 4 Penn State won at Boston College 29–0, and No. 5 Notre Dame was upset at unranked Michigan State, 21–17. No. 6 Tennessee, which had reached 4–0–1 the week before with a 10–9 win over Alabama, moved up in the rankings. The next poll was No. 1 USC, No. 2 Ohio State, No. 3 Kansas, No. 4 Penn State, and No. 5 Tennessee.

November 2 No. 1 USC won at Oregon, 20–13, and No. 2 Ohio State beat No. 16 Michigan State 25–20. No. 3 Kansas posted its seventh win, over visiting Colorado, 27–14. No. 4 Penn State slipped past Army, 28–24 and No. 5 Tennessee beat visiting UCLA 42–18. The top five remained the same.

November 9 No. 1 USC turned back No. 11 California 35–17, and No. 2 Ohio State stayed unbeaten as well, downing Wisconsin 43–8. No. 3 Kansas, however, lost to unranked Oklahoma, 27–23. No. 4 Penn State beat visiting Miami (FL) 22–7, but No. 5 Tennessee lost to No. 18 Auburn in Birmingham, 28–14. No. 7 Michigan, riding a seven-game winning streak after losing their opener to California, won 36–0 over Illinois. No. 9 Georgia, which had been tied by Tennessee and Houston but was otherwise unbeaten, defeated Florida 51–0 in Jacksonville. The next poll was No. 1 USC, No. 2 Ohio State, No. 3 Penn State, No. 4 Michigan, and No. 5 Georgia.

November 16 No. 1 USC beat No. 13 Oregon State 17–13 and effectively clinched a Rose Bowl bid; the Beavers had been USC's only remaining rival for the Pac-8 title and this victory gave the Trojans the head-to-head advantage. No. 2 Ohio State won at unranked Iowa 33–27. No. 3 Penn State won its eighth straight at Maryland 57–13, and No. 4 Michigan beat Wisconsin 34–9. No. 5 Georgia won 17–3 at No. 12 Auburn. The top five remained the same.

November 23 No. 1 USC beat UCLA 28–16 to stay unbeaten and clinch an outright Pac-8 championship. No. 2 Ohio State, which also had an unblemished record, hosted No. 4 Michigan. In what would become a recurring pattern over the next decade, both teams were unbeaten in conference play and the game would determine who would represent the Big Ten in the Rose Bowl. Coach Woody Hayes' Buckeyes triumphed 50–14 over the Wolverines. No. 3 Penn State traveled and crushed Pittsburgh 65–9. No. 5 Georgia was idle. No. 7 Kansas finished its season with a 21–19 win at No. 13 Missouri. Kansas' only loss was to Oklahoma, their co-champions in the Big 8; the Jayhawks, who were ranked higher and had a better overall record than the Sooners, were chosen for the conference's spot in the Orange Bowl.

In the polls released on November 25, there was a disagreement between the AP writers and the UPI coaches as the AP made Ohio State its new No. 1.^[2] Though USC had more first place votes than Ohio State (24½ vs 21½), the Buckeyes were 10 points ahead overall in the AP poll (935–925). In the UPI poll of coaches, however, USC remained in first place and Ohio State second. (332–321 in total points). Both polls rounded out the top five with No. 3 Penn State, No. 4 Georgia, and No. 5 Kansas.

Also this week, Yale and Harvard (both of which were undefeated) met and ended their game in a 29–29 tie. The game was the basis of Harvard Crimson newspaper headline (and later the title of a documentary) Harvard Beats Yale 29–29.

November 30 No. 1 Ohio State and No. 5 Kansas had finished their seasons, and No. 3 Penn State was idle. No. 2 USC was tied by visiting No. 9 Notre Dame, 21–21. No. 4 Georgia closed its season unbeaten at 8–0–2, with a 47–8 win at home over Georgia Tech. As the SEC champs, the Bulldogs went to the Sugar Bowl against SWC co-champion Arkansas. No. 6 Texas finished their season with a 35–14 victory over Texas A&M. After a loss and a tie in their first two games, the Longhorns won their final eight in a row, including a 39–29 win over Arkansas. The head-to-head victory gave Texas the conference's Cotton Bowl bid against SEC runner-up Tennessee.

The AP's final regular season poll was No. 1 Ohio State, No. 2 USC, No. 3 Penn State, No. 4 Georgia, and No. 5 Texas. Ohio State had 34 of the 39 first place votes cast. Following USC's 9–0–1 finish, the UPI coaches voted unbeaten and untied (9–0) Ohio State as the national champion in their final poll on December 3. At the time, the UPI did not do a poll following the postseason bowl games, and the result would have been unaffected by the OSU and USC meeting in the Rose Bowl. The result was 28 first place votes (and 334 points) for OSU, and only 4 first place (and 277 points) for USC.^[3]

In the only significant regular season game played after the polls were taken, No. 3 Penn State remained undefeated by beating Syracuse 30–12 on December 7. The Nittany Lions prepared for a matchup against Kansas in the Orange Bowl.

The Heisman Trophy is given to the year's most outstanding player

Source: ^[5]

• 1968 NCAA University Division football rankings
• 1968 NCAA College Division football season
• 1968 College Football All-America Team