MetaMask USD (mUSD) is a cryptocurrency stablecoin introduced by MetaMask in September 2025. Issued by Bridge and utilizing the M0 protocol, it stands as the first stablecoin produced by a self-custodial wallet. Stablecoins are tokens engineered to keep a consistent value by linking to less fluctuating assets, such as the US Dollar.

The mUSD token is secured by short-term US Treasury bills kept in regulated custody and distributed via a structure built by Bridge.xyz on the M0 protocol. For each 1 mUSD in circulation, a corresponding dollar-backed asset is held in reserve.

mUSD debuted on Ethereum Mainnet (EVM) and Linea, an EVM Layer 2 network where the token serves a central function. Its integration covers core EVM protocols, lending markets, decentralized exchanges (DEXs), and custodial platforms. Users can employ mUSD for smooth fiat-to-crypto onramps, swaps, trades, and decentralized finance (DeFi) activities. Additionally, mUSD is spendable at Mastercard merchants globally through the MetaMask Card.

As a wallet-native stablecoin, mUSD aims to streamline the crypto experience within MetaMask, covering onramping, holding, earning, and spending. It allows users to transition between blockchain ecosystems more effectively. Stablecoins such as mUSD are essential to DeFi, supporting trading, lending, and remittances, while also acting as a connector between traditional finance (TradFi) and DeFi ecosystems.