Tether (USDT) is the largest stablecoin cryptocurrency. It is pegged to the US Dollar. (1 USDT=$1 USD) Each Tether token that is issued is backed by $1 USD that is supposedly held in reserve. Tether has been the subject of some controversy because they have failed to allow a transparent audit of their currency reserves.
Tether facilitate transactions between cryptocurrency exchanges at a rate that is fixed to the United States dollar. This allows traders to take better advantage of arbitrage opportunities. Tether was created by the leaders of Bitfinex, one of the largest crypto exchanges.

STASIS EURO is an Ethereum-based stablecoin that is pegged to the Euro. Each STASIS EURO token is backed 1:1 with Euros held in a reserve account. The STASIS EURO was created by STASIS to power their tokenization platform. EURS can be issued in exchange for securities, which are purchased by STASIS’ liquidity providers. The EURS token is supported by an ecosystem of liquidity providers and exchanges.

Paxos is a regulated financial company specializing in providing blockchain trust and custodial services for their clients. Paxos' settlement platform (Bankchain) is designed to be integrated with existing systems and to eliminate settlement risk in the exchange of digital assets. The company created a USD backed stablecoin called PAX, that is built on the Ethereum blockchain, and is meant to assist their clients in converting a variety of assets into digital versions, that can be more easily exchanged on a blockchain.