UMA, an acronym for Universal Market Access, is a decentralized financial contracts platform that strives to enable universal market access. It is an optimistic oracle (OO) that has the potential to record any verifiable truth onto a blockchain. This unique feature has led to UMA's OO being referred to as a "human-powered truth machine". It is designed to be flexible enough to handle ambiguity and expands the design space possible in web3. UMA's OO is used in a diverse ecosystem of web3 applications, including cross-chain bridges, insurance protocols, prediction markets, and customizable DAO tooling products.

UMA operates through an optimistic oracle system that verifies data in stages. Initially, a statement is proposed as true and submitted along with a bond. This bond acts as a bounty for anyone to dispute it if they have evidence to the contrary. If the statement is not disputed during the challenge period, it is accepted as true. If a dispute arises, UMA token holders resolve the dispute within 48 hours. If the disputer is right, they receive a portion of the proposer's bond; if the disputer is wrong, they lose their bond, a portion of which is given to the proposer. This system introduces the opportunity for human intelligence to weigh in, which is crucial for Web3 projects as they require arbitrary data that is not always possible to turn into code.

UMA's optimistic oracle system may have a range of potential use cases. It can be used to enable more trustless forms of DAO governance, as seen in the first product using this, oSnap, which is a trustless method to execute the results of a Snapshot vote on chain. UMA can also be used in prediction markets, insurance protocols, cross-chain communication, and real-world assets. Furthermore, UMA's smart contracts can be used by developers building decentralized applications, and UMA token owners have the ability to participate in UMA’s optimistic oracle.

UMA was founded in 2018 by Allison Lu and Hart Lambur, two ex Goldman Sachs traders. Their goal was to make global markets universally fair, accessible, and decentralized. The team drew inspiration from traditional finance derivatives to define an open-source protocol that allows anyone, anywhere, to design and build trustless financial contracts. The optimistic oracle design concept has been in development since 2014, when Vitalik Buterin first published on the matter. Over the years, there have been several iterations leading to the current design of UMA's optimistic oracle. As of September 2022, there was a supply of 108,858,567 UMA tokens with 68,947,415 in circulation.