Tether (USDT) is a stablecoin pegged to the U.S. dollar, making it the third-largest cryptocurrency after Bitcoin and Ethereum. It is issued by iFinex, a Hong Kong-registered company that also owns BitFinex. As of March 2024, USDT was the third-largest cryptocurrency after Bitcoin and Ethereum, and the largest stablecoin with a market capitalization of nearly $99 billion.

Tether is part of a fast-growing type of cryptocurrency called stablecoins, which avoid the extreme volatility of untethered cryptocurrencies. The company was launched as RealCoin in July 2014 and rebranded as Tether in November 2014. As of March 3, 2024, Tether reported assets of $99.45 billion for USDT, holding 84.58% of its reserves in cash, cash equivalents, short-term deposits, and commercial paper.

Tether has faced several challenges in its history, including the electronic theft of $31 million in USDT tokens in November 2017, a court order enjoining Tether and BitFinex parent iFinex from further violations of New York law, and a settlement with Bitfinex in February 2021. In October 2021, Tether agreed to pay a $41 million fine over claims that Tether stablecoin was fully backed by U.S. dollars.

In 2023, Tether expanded into artificial intelligence by acquiring Northern Data Group and appointed a new CEO, Paolo Ardoino. A lengthy lawsuit against Tether and Bitfinex was concluded in November 2023. The company continues to participate in measures to enhance cryptocurrency security, educate users and legislators, and cooperate with law enforcement agencies.