Beinwil Abbey (Kloster Beinwil) was a Benedictine monastery in Beinwil in the Canton of Solothurn in Switzerland.
It was founded in 1085, probably by the local nobility. After conflicts arising from the territorial claims of the towns of Solothurn and Basle against the Counts of Thierstein, who acted as the abbey's Vögte (lords protectors), it was burnt down in 1445. After Beinwil had been taken over by Solothurn in 1519, the town authorities impounded much of the abbey's possessions.
By the 16th century only a few monks were left in the abbey, and it was formally dissolved in 1554. A small community remained, the care of which was assumed firstly by Einsiedeln Abbey, in 1589, and then, from 1622, by Rheinau Abbey. As no monastic revival could be achieved in the remoteness of its situation, it was decided to re-settle the community at Mariastein Abbey, a new foundation in a pilgrimage centre, which took place in 1648. In anticipation of this, Mariastein became a member of the Swiss Congregation, now part of the Benedictine Confederation. From Mariastein, at the end of the 18th century, it was at length possible to revive Beinwil, and at that time the church and the monastic premises were rebuilt.
The abbey was however suppressed in 1874 by plebiscite during the Kulturkampf, and the community of Mariastein went into exile.
The abbey church, dedicated to Saint Vincent of Saragossa was destroyed by fire in 1978. It has now been comprehensively restored and a high altar has been installed, dated about 1700, from Bellwald. Today the former abbey is used as an ecumenical conference and retreat centre.