Biggest Betting Upsets This Year

Every year produces a handful of results so improbable that the betting market essentially said 'no chance' — and then reality walked in anyway. This page tracks the biggest upsets of 2026, ranked by what $1 placed at the pre-event odds would have returned. We update it as new chaos happens.

An upset, for our purposes, is any outcome where the implied probability was below 10% — meaning the market thought there was less than a one-in-ten shot of it happening. The lower the pre-event probability, the bigger the payout, and the more dramatic the upset. We pull from both sports betting markets and prediction market platforms like Kalshi.

Upsets aren't just fun stories. They're evidence that markets — which are supposed to be efficient — get things wrong regularly. The crowd is usually right about the direction but routinely misprices the magnitude. A team given a 3% chance still wins roughly 3 times out of 100. Over a full year, across thousands of markets, a few of those 3% shots will connect. The question is which ones.

We frame every upset through the $1 lens because it makes the improbability concrete. When someone says a team was a 'massive underdog,' that's vague. When you say '$1 would have paid $45,' that's specific. You can feel the gap between what the market expected and what actually happened. The bigger the number, the harder the market flinched.

If you look at previous years' biggest upsets, a few patterns emerge. Sports upsets tend to cluster in the early rounds of tournaments, where top seeds face unknown opponents and the line is set by reputation more than form. Prediction market upsets tend to involve political events that shift faster than the market can reprice — resignations, surprise policy moves, weather events that beat the model.

Check the Dollar Bets homepage for today's live markets, including current longshots that might end up on this list by December. We color-code every payout from green (respectable) to purple (generational), so the potential scale of any upset is visible at a glance. If something lands on this page, it started as purple.