This article answers which horse is the biggest underdog to win the Kentucky Derby, and explains the method historians use to make that comparison. It gives a short, sourced answer up front and then walks through pari-mutuel mechanics, the ranking methodology, a top-five payout list, and short case studies of the most notable upsets. If you want a quick takeaway: Donerail remains the all time longest-priced winner by $2 payout, while Rich Strike is the most prominent modern longshot. The sections that follow explain why those payouts matter and where to verify the official figures.

Donerail, in 1913, holds the record for the largest $2 win payout in Kentucky Derby history.

Rich Strike's 2022 victory is the modern benchmark longshot, paying $163.60 on a $2 win ticket.

Historians rank Derby longshots by the official $2 win payout because it reflects the pari-mutuel market outcome.

Quick answer: which horse is the biggest underdog to win the Kentucky Derby?

Short answer, by the standard historians and race authorities use: Donerail remains the biggest underdog to win the Kentucky Derby, winning in 1913 at roughly 91 to 1 and paying $184.90 on a $2 win bet, a figure preserved on the official Derby history page for that race Kentucky Derby history page for Donerail.

In modern times the most-cited benchmark longshot is Rich Strike, which won the 2022 Kentucky Derby at about 80 to 1 and returned $163.60 on a $2 win bet as shown in the official race accounts and chart Kentucky Derby history entry for Rich Strike.

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Read the full breakdown below for sourced context, the ranking method, and practical tips for checking official payouts and race charts.

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When lists of all-time Derby longshots are compiled, historians and industry summaries usually rank winners by the official $2 win payout rather than raw fractional odds, because the payout reflects the pari-mutuel outcome on race day and allows cross-era comparison America's Best Racing roundup of longshot Derby winners.

How Kentucky Derby odds and payouts are set: pari-mutuel basics

Most public betting on the Kentucky Derby is pari-mutuel, which means bettors wager into shared pools and the final odds and payouts are calculated from how money is distributed in those pools, after the track removes a takeout portion Pari-mutuel overview at Encyclopaedia Britannica.

In practical terms that means odds are a real-time reflection of where money goes, not a fixed price set by a bookmaker. As betting flows change before and during a race the displayed odds move, and the final $2 win payout is determined after pools close and the takeout is deducted, then the remaining pool is divided among winning tickets.

Takeout rates and total pool size matter because they change the effective payout per dollar wagered. A relatively small pool supporting a longshot winner will result in a larger per-ticket payout than a deep, widely distributed pool backing the favorite, all else equal.

Close up of vintage two dollar Donerail betting payoff slip on dark Funded Plays background archival paper texture realistic lighting showing payoff numbers and rich strike odds

Official race authorities publish the final $2 win payout and the official chart after each race, and historians use those reported $2 win figures when ranking the biggest underdogs across different decades Kentucky Derby official records.

What pari-mutuel means

Pari-mutuel is a shared-pool system where bettors win from the pool, and the odds reflect the crowd's distribution of money rather than a fixed offer by a bookmaker. The system is why unexpected upsets can produce very large payoffs when relatively few winning tickets share the pool Pari-mutuel overview at Encyclopaedia Britannica.

How takeout and pool distribution affect the $2 win payout

Takeout is the track and state deductions from the pool that are removed before payouts are calculated. Higher takeout reduces the total amount available to pay winners, and the pattern of where money sits in the pool determines the per-ticket payout for the winning horse.

What counts as the 'biggest underdog': methodology for comparing winners

For clarity, this article treats the biggest underdog as the horse that produced the largest official $2 win payout as recorded by race authorities, because that payout captures the pari-mutuel market outcome on race day and is the accepted cross-era measure.

Raw odds like 91 to 1 are useful shorthand, but they do not always map perfectly to payouts because of pool size and takeout. Using the $2 payout avoids distortions that come from comparing fractional odds across eras with different betting environments.

What is the biggest underdog to win the Kentucky Derby?

By the standard $2 win payout used for cross-era comparison, Donerail is the biggest underdog, with Rich Strike the modern benchmark due to its 2022 payoff.

That $2 payout approach is standard in consolidated lists and industry summaries that rank Derby longshots by how much they returned to a standard $2 win ticket, which is why modern summaries quote a ranking by $2 payout rather than by the fractional odds alone America's Best Racing longshot list.

Raw odds versus official $2 win payout

Raw odds express a ratio, while the $2 win payout tells how much a typical $2 ticket actually returned after the pari-mutuel calculation. That makes $2 payouts better for comparing winners from 1913 to the 2020s, since betting behavior and takeout policies have changed.

Why $2 payout is the standard cross-era measure

Histories and official race pages publish the $2 win number consistently, so it is practical and verifiable. When authorities and consolidated historical lists cite the biggest underdogs they point to the published $2 win payouts as the primary ranking metric Kentucky Derby official records for modern winners.

Top Kentucky Derby longshots by $2 win payout: an all-time list

Authoritative consolidated lists name the top five Kentucky Derby longshot winners by $2 win payout as Donerail, Rich Strike, Country House, Mine That Bird, and Giacomo, a ranking used by historians and industry summaries America's Best Racing list of longest shots.

The ranking is based on the official $2 win payouts reported at the time by the race authorities, and it remains valid into 2026 because no subsequent winner has recorded a larger official $2 win payout than those listed.

1. Donerail, 1913. Reported odds of about 91 to 1, official $2 win payout $184.90, recorded on the Kentucky Derby history page as the highest all-time payout Kentucky Derby history page for Donerail.

2. Rich Strike, 2022. Approximately 80 to 1 in reported odds, with the official $2 win payout of $163.60 as shown in the race record and chart Equibase official chart for the 2022 Kentucky Derby.

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3. Country House, 2019. Around 65 to 1 with a $2 win payout of $132.40, listed in Derby history pages and in consolidated longshot rankings Kentucky Derby history entry for Country House.

4. Mine That Bird, 2009. A widely cited modern upset that appears among the top five payouts in consolidated lists, with the specific ranking based on the published $2 payout at the time America's Best Racing longshot roundup.

5. Giacomo, 2005. Another modern upset included in the top five on consolidated payout-based lists, placed by its official $2 win number relative to the others on established summaries America's Best Racing longshot roundup.

When payouts are close, historians prefer the concrete $2 number because it is a standard, verifiable figure that already accounts for pool size and takeout, which raw odds alone do not.

Case study: Rich Strike (2022) - the modern benchmark longshot

Rich Strike's 2022 Kentucky Derby win stands out because it combined an unusually late surge with a race-day market that left him near the bottom of the betting pools, producing an official $2 win payout of $163.60 that ranks him among the largest modern payoffs Kentucky Derby history entry for Rich Strike and the Equibase horse profile Equibase horse profile for Rich Strike.

rich strike odds

The public reported roughly 80 to 1 odds before the race, a position reflected in both Derby summaries and the official race chart, and the pari-mutuel outcome produced the $163.60 payoff because relatively few tickets backed Rich Strike compared with the favorites Equibase race chart for the 2022 Derby and the Equibase chart PDF Equibase chart PDF. See the public summary on Rich Strike on Wikipedia for a consolidated overview.

Quick chart checks to verify official payouts

Race date
Winner
$2 payout
Source

Use official charts for confirmation

Race-day dynamics that influence such a payoff include late scratches, shifting support for other runners, and in-race developments that leave a longshot with a small share of the pool. These are market factors, not claims about the horse's inherent quality, and are why payout-based rankings reflect the day, not a definitive measure of ability.

For readers who want the primary documents, the official Kentucky Derby history entry and the Equibase race chart are the reference points that record the final odds and the $2 payout for every Derby edition Kentucky Derby history page for Rich Strike.

Case study: Donerail (1913) - the longest-priced Derby winner

Donerail's 1913 victory is the longest-priced Kentucky Derby win on record, with contemporary sources recording about 91 to 1 odds and an official $2 win payout of $184.90, a figure retained in the Derby's historical record Kentucky Derby history page for Donerail.

That result remains the top benchmark because official records publish the $2 payout and historians use it to compare across eras, despite changes in betting patterns and pool sizes that have occurred over the last century.

While early 20th-century recordkeeping differs from modern electronic charts, the Kentucky Derby's official history is the primary source for Donerail's numbers and is the basis for continued placement at the top of payout-based lists.

Minimal vector illustration of Rich Strike galloping past stylized Churchill Downs twin spires with a modest payout coin stack graphic indicating rich strike odds

Case study: Country House (2019) and other notable modern upsets

Country House's 2019 Kentucky Derby win is among the modern upsets that register as large payouts, with an official $2 win payout of $132.40, placing it high in consolidated lists of longshot winners Kentucky Derby history entry for Country House.

Mine That Bird in 2009 and Giacomo in 2005 also appear in modern longshot lists based on their official payouts, and they are commonly listed alongside Country House and Rich Strike in payout rankings that track the biggest Derby upsets America's Best Racing longshot compilation.

Common mistakes when reading longshot results and what to watch for

One common mistake is equating a large payout with consistent value. A single longshot win produces a headline payoff, but it does not prove a repeatable edge, because the payout depends on how money was distributed in the pari-mutuel pool that day.

Another pitfall is using raw odds alone for cross-era comparisons. Odds tell a ratio at a moment in time, but the $2 payout accounts for pool size and takeout, which makes it more reliable for comparing winners from different decades America's Best Racing explanation of longshot rankings.

When verifying claims, consult the official race chart and the Derby history page for the exact published $2 win payout and the reported odds rather than relying on secondary summaries alone Equibase official chart source.

Practical takeaways for fans, bettors, and historians

Check KentuckyDerby.com for the official history entry and Equibase for the race chart when you need the authoritative $2 win payout or the official odds for a particular Derby edition Kentucky Derby official records.

Remember that payout-based rankings use the $2 win number because it is standardized and publicly posted, making it the practical cross-era metric to identify the biggest underdogs in Derby history.

How is the biggest Kentucky Derby underdog determined?

Histories and analysts use the official $2 win payout reported by race authorities to rank underdogs, because it reflects the pari-mutuel outcome on race day and allows cross-era comparison.

Did Rich Strike have the highest odds ever?

Rich Strike was a modern longshot with about 80 to 1 odds and a large $2 payout, but Donerail's 1913 payout remains the all time highest by $2 win payout.

Where can I verify official Derby payouts?

Check KentuckyDerby.com for the official race history entries and Equibase for the detailed race charts and published $2 win payouts.

Use official Derby history pages and Equibase race charts when you need to confirm payouts or check how a particular upset unfolded. Payout-based rankings document what happened in the betting pools on race day, which is the practical measure historians use to identify the biggest underdogs. If you track patterns or study upsets, keep in mind that large payoffs are rare outcomes of pari-mutuel markets and do not by themselves establish a repeatable prediction edge.