First I have been a fan since the 1968 season when I was 6 years old. So this potential list goes back 56 years.

Second how do I define worst loss? To me losing to a ranked team, regardless of score, although greatly disappointing cannot be a "worst" loss. ie the other team was a good team and we came up short that day. So you won't see the loss to Clemson (any of them) losses to UM the previous 3 years, losses in the playoffs or major bowls etc

To me a "worst" loss, is a loss to a vastly inferior team and that loss had to cost you something in the end, ie a B10 title, a shot at the national title. so games like the 1974 loss to MSU does not qualify as OSU would end up losing the Rose Bowl that year anyway.

So here goes from oldest to newest.

1993 - UM (0-28) - Lost away while ranked #5 with an outside shot at a national title to a 6-4 UM team. The loss cost us an outright B10 title and caused us to go to Holiday Bowl instead of a major bowl. We would finish ranked 11th.

1998 - MSU (24-28) - Lost at home while ranked #1 to a 4-4 MSU team. Dropped us to #7 and it cost us a National Title shot and an outright B10 title, we would finish ranked #2

2017 - Iowa (24-55) - Lost away while ranked #3 to a 5-3 Iowa. Cost OSU a playoff spot, as we dropped to #11 after the game. Would finish ranked 5th

2018 - Purdue (20-49) - Lost away when ranked #2 to a 3-3 Purdue team. Cost OSU a playoff spot as they dropped to #8 after the game. Would finish ranked 5th

2024 - UM (10-13) - Lost at home while ranked #2 to a 6-5 UM team. Cost us a potential B10 title and dropped us at least 3 spots in the NCAA tourney field. Dropped to #6 after the game, final outcome to be determined.

If I had to rank these from Worst to least worst it would be:

1998 - The worst due to directly costing OSU a shot at a National Title. MSU would finish 6-6 and OSU would easily win out beating 2 ranked teams in the final 3 games

2024 - in part due to UM and the 4th straight loss but had this not been a 12 team field this would have cost us a playoff spot just like 17 and 18 did, or like 1998 when no playoff would have cost us any shot at a national title. so these 2 are very close for the worst loss.

2018 - Purdue was a bad team who would lose 4 of their last 6 games, The hang over from this loss lasted 3 more weeks as we struggled to get past Nebraska and MD in 2 of the next 3 games never allowing us to improve our ranking and thus missed a playoff shot as we were technically underdogs in The Game and were ranked 6th going into the B10 CG which we would win but not in a blowout over NW as it was a 1 score game with less than 10 mins left

2017 - Iowa was better than we often give credit to as they were 5-3 but would finish 8-5 and win a bowl. Still a lopsided loss to a team they should have beaten and again cost them a shot at the Title as we fell 8 spots. And although we won out we finished 5th and just missed the playoffs

1993 - Mainly due to us being ranked #5 with barely a shot at national title, this loss coast the least.

1996 UM of course would be on this list except that UM was ranked entering that game at 7-3. So massively disappointing, but not a "worst" loss by my definition.