Barbara Baths, Roman thermal complex in Trier, Germany.

The Barbara Baths comprise a vast Roman bathing complex spread across a large site that reveals how Romans organized their facilities. The structure features multiple bathing pools at different temperatures, changing rooms, and spaces for exercise or leisure.

The Barbara Baths were built in the second half of the 2nd century, when the Forum Baths had become too small for Trier's growing population. The complex covered 172 by 240 metres, two city blocks and a street, and was supplied by the Ruwer aqueduct. Coins and pottery show use until the end of the 4th century; the baths closed with Trier's destruction in the early 5th century.

The name comes from the parish church of St. Barbara, which stood nearby; the baths themselves gave rise to the suburb of St. Barbara. Visitors can still see early Christian grave inscriptions that point to a church, possibly from Merovingian times, built within the ruins.

The ruins stand within Trier, a short walk from the start of Friedrich-Wilhelm-Straße, where the footbridge over the complex begins. The site is open at set hours with no admission fee, and the bridge carries information panels. The ruins were closed for restoration from 2000 until 23 July 2015.

The underground heating system was remarkably advanced, using warm air that circulated beneath the floors to heat entire rooms. This principle allowed Romans to maintain comfortable temperatures over long periods while using relatively little fuel.