Who will be the Lightweight Title Holder on Dec 31, 2026
Leader sits at 91% across 4 bound outcomes, runner-up at 9%. This is a winner-take-all market — the headline is the leader’s price, not an arithmetic mean.
Leader probability
Justin Gaethje
Outcomes
4
winner-take-all
Runner-up
9¢
Mauricio Ruffy
Spread
82pp
dominant leader
24h volume
$6K
modest
Closes
Dec 31, 2026
101 days
Venue
Kalshi
4 bound
30-day trend
Bracket family
How the bracket ladder is priced.
Each row is one outcome on the venue. Sorted by 24h volume — the heaviest book is at the top.
Cluster 1
Who will be the Lightweight Title Holder on Dec 31, 2026
Who will be the Lightweight Title Holder on Dec 31, 2026?: Arman Tsarukyan
KXUFCLIGHTWEIGHTTITLE-26-ATSA
Who will be the Lightweight Title Holder on Dec 31, 2026?: Ilia Topuria
KXUFCLIGHTWEIGHTTITLE-26-ITOP
Who will be the Lightweight Title Holder on Dec 31, 2026?: Justin Gaethje
KXUFCLIGHTWEIGHTTITLE-26-JGAE
Who will be the Lightweight Title Holder on Dec 31, 2026?: Mauricio Ruffy
KXUFCLIGHTWEIGHTTITLE-26-MRUF
Analysis
This probability estimates that Justin Gaethje will hold the UFC Lightweight title on December 31, 2026. The 92% price reflects his current status as champion, with roughly four months remaining for the title to change hands through either a scheduled bout or unexpected circumstances. The main drivers of this level are the typical timeline for title defenses in the UFC and the competitive field among challengers. The biggest catalyst would be any scheduled lightweight title fight before year-end; if no fight is announced in the coming weeks, the probability would likely remain elevated. Conversely, if Gaethje is booked against a top contender with a short turnaround, market pricing could shift based on fighter odds and injury risk.
- ›Gaethje must defend or retain the title through December 31, 2026—roughly 3.5 months away
- ›UFC title fights typically require 2-3 months of notice; lack of an announced bout suggests low probability of a defense occurring before year-end
- ›The runner-up probability (4%) suggests one specific contender or outcome; identify which challenger is being priced as most likely to dethrone Gaethje
- ›Injury or medical suspension of Gaethje or any scheduled challenger would directly affect both the title holder outcome and timeline
- ›Historical UFC lightweight title vacancy patterns and typical defense frequencies inform baseline expectations for divisional activity
What moved the line
- Sep 17Mauricio Ruffy↑5pp4→9¢ · Kalshi
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These markets stopped trading. Last odds and any captured outcome are shown above — full settlement detail lives at the venue.
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How we compute these odds
SimpleFunctions aggregates live prediction-market contracts from Kalshi and Polymarket. Each slug groups contracts that resolve on the same underlying event, identified by venue event_id.
For binary slugs, the headline probability is the liquidity-weighted mid-price across all bound contracts. For multi-outcome slugs (e.g. elections with 3+ candidates), the headline is the leader’s price; we never arithmetically average disjoint outcomes — that would produce a number with no real-world meaning.
Snapshots refresh every 5 minutes during market hours; daily aggregates are computed at 04:00 UTC. The 30-day sparkline is drawn from per-ticker daily means stored in market_indicator_daily; 24h delta and movement events are derived from the same source.
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