German piano builder, and also a maker of organs and harpsichords, who was the first of a distinguished family of piano makers.

The son of an organ builder, Stein apprenticed with the famous instrument maker Johann Andreas Silbermann in 1748–49. For a time he evidently lived in Paris, but he was most active in Augsburg, where he was a church organist as well as an instrument maker.

W.A. Mozart in 1777 enthusiastically described a Stein piano on which he had played. Among its features were knee levers for raising the dampers (the function of the far right pedal on modern pianos) and a cleverly devised and sensitive mechanism for setting the hammers in motion (escapement action). After about 1770 Stein's action, or key mechanism, was widely copied in Germany and became the model for the Viennese action. Several of his pianos have been preserved in museums and by private owners.

After Stein's death his daughter Maria Anna (Nannette; 1769–1833) and son Matthäus Andreas (1776–1842) continued his business; Matthäus began working independently in 1802. Nannette, who was a talented pianist, moved with her husband, the noted pianist Johann Andreas Streicher, to Vienna. Stein's son Friedrich (1784–1809) was an excellent pianist.

Matthäus' son Karl Andreas (1797–1863) was widely known as a pianist, teacher, composer, and piano maker to the court in Vienna. Nannette's son Johann Baptist Streicher became the head of a family of musicians and piano makers that continued into the 20th century.