Polymarket is an American cryptocurrency-based prediction market which offers a platform where individuals can place bets on future outcomes, including sports matches, economic indicators, weather patterns, awards, political and legislative outcomes, and military conflicts. Participants can deposit cryptocurrency through the Polygon blockchain network and trade shares that represent the likelihood of specific future outcomes. The company is headquartered in Manhattan, New York City, where the platform was launched in 2020, and has legal domicile in Panama.

The platform has been described as operating in "a legal and ethical grey area" because of the controversial nature of the betting markets offered by the company, including markets related to military strikes and ongoing wars. The majority of trades on the platform are related to sports. While it is not labelled a sports betting platform, 63% of trades on the platform are for sports bets. Instances of insider trading and attempts to manipulate outcomes have been observed on the platform.

Polymarket has been banned by the governments of France, Brazil, Italy and Gibraltar. It was not able to operate in the United States from 2022 until 2025, when the second Donald Trump administration eased the regulatory environment and Donald Trump Jr. joined the company as an advisor.

Founded in 2020 by Shayne Coplan, Polymarket is a prediction market that allows users to gain/lose on the outcome of world events. In January 2022, Polymarket was fined US$1.4 million by the Commodity Futures Trading Commission (CFTC), and received a cease-and-desist order for regulatory violations, including failure to register as a Swap Execution Facility. According to the CFTC, Polymarket offered "substantial cooperation" throughout the investigation, which resulted in the company receiving a lower fine.

In May 2022, Polymarket appointed J. Christopher Giancarlo, a former commissioner of the CFTC, as chairman of its advisory board. In May 2024, the company announced that it had raised $70 million across two funding rounds. These rounds included investments from Vitalik Buterin, the cofounder of Ethereum, and Founders Fund, a venture capital firm founded by Peter Thiel.

In June 2023, Mother Jones reported that interest in the company had increased after a tweet about the outcome of the Titan submersible went viral; the premise of the bet was whether the submersible would be found by a certain date, rather than a wager on the fate of the passengers. Polymarket had over 60 markets available at the time of the submersible wager, including the outcome of the Guatemalan presidential election, the likelihood of Twitter suing Meta, and the likelihood that Russia would use nuclear force.

In 2024, the outcome of U.S. elections became the most active market on the platform, with over $3.3 billion (as of November 5, 2024) wagered on the presidential race between the Republican candidate Donald Trump and Democratic candidate Kamala Harris. Nate Silver, founder of polling analysis firm FiveThirtyEight, became an advisor to Polymarket in 2024.

A few days after the 2024 U.S. presidential debate held on June 27, 2024, Polymarket predicted a 70% chance that Democratic candidate Joe Biden would withdraw from the 2024 U.S. presidential election race (an increase from 20%), weeks before he officially announced his withdrawal. By contrast, on August 5, Polymarket showed 68% odds Kamala Harris would pick Pennsylvania governor Josh Shapiro as her running mate, with Minnesota governor Tim Walz at 23% odds. Harris selected Walz the next day.

On October 7, 2024, Polymarket showed a spike in the odds Donald Trump would win the 2024 election, to 53.3%, with a corresponding decline in Kamala Harris's odds, to 46.1%. Two Polymarket competitors continued to show Harris with better odds of winning, at about 51%; Polymarket also showed a slight edge for Harris throughout September. That day, the FiveThirtyEight simulation model found Harris had a 55% chance to win the election, while elections statistician Nate Silver said his model gave Harris 54.7% odds.

Forbes reported on theories for the Polymarket divergence, including that one or more major wagers had been placed on Trump, possibly because Elon Musk had spoken at a Trump rally two days earlier, and had previously promoted Polymarket. On the day of the Trump spike, Musk reposted an X post that asserted "Kamala is collapsing before our eyes." However, due to Polymarket lacking a cap on individual investor amounts, large wagers by one or a few bettors may not reflect a material change in the election landscape.

Silver, a Polymarket advisor, said the shift in Trump's favor was a "larger swing than is justified." Polymarket competitor PredictIt had since shown Trump with better odds of winning after previously favoring Kamala Harris.

The second Donald Trump administration eased the regulatory environment for Polymarket. In July 2025, the Commodity Futures Trading Commission (CFTC) and Department of Justice ended a probe into Polymarket. The CFTC under the Joe Biden administration had entered into a settlement with Polymarket whereby Polymarket agreed to wind down U.S. operations after being accused of running an illegal exchange. In 2025, Donald Trump Jr., a member of the Trump family, has taken on an advisory role at Polymarket, after his firm 1789 Capital invested in Polymarket.

Polymarket allows bets on armed conflicts, which has led to members of armed forces placing bets on operations, impacts on war reporting, and bets about nuclear war. War bets may rely on classified military information. According to the Anti-Corruption Data Collective, 52% of military action long-shot bets—defined as those worth $2,500 or more with odds at or below 35%—are successful, compared to 25% for politics bets and 14% of all bets.