Austrian builder of pianos (piano) and founder of the firm that bears his name.

Bösendorfer served an apprenticeship with the Viennese piano maker Joseph Brodmann. After Franz Liszt began using Bösendorfer's instruments, his company gained international fame, and Bösendorfer was formally recognized by the Austrian emperor as imperial piano-manufacturer in 1830.

Bösendorfer experimented with a variety of actions (mechanisms whereby the finger's pressure is transmitted to a padded hammer and thence imparted to the strings), using different action designs for his smaller and largest grand pianos. The imperial grand, his largest size, had the extraordinary compass of eight octaves; later, it was shortened to the standard seven and one-half. The modern Bösendorfer concert grand is more than 3 m (9 feet) long and is highly prized for its tone.

Bösendorfer was succeeded in his business by his son Ludwig, who in 1872 built the Bösendorfer Hall in Vienna, a centre for the performance of chamber music and piano recitals. After Ludwig's death in 1919, the business passed into other hands.