Les Guitares bien tempérées (The Well-Tempered Guitars), Op. 199, for two guitars, is a work written in 1962 by Mario Castelnuovo-Tedesco. It consists of 24 pairs of preludes and fugues, one pair in each of the 24 major and minor keys. The 24 pieces are divided into four books. It has been described as the longest and most important cycle of works ever composed for two guitars. It was both inspired by and a tribute to Johann Sebastian Bach's The Well-Tempered Clavier, a work for solo keyboard.