Muzio Clementi (1752-1832) was an Italian-born English pianist, composer, teacher, and conductor among many other things. Out of his considerable compositional output, his sonatinas in particular have enjoyed considerable success and are widely used even to this day in piano teaching.
The sonatina featured here is the first and the easiest of the six contained in his Op. 36. For this reason, this is usually one of the very first sonatinas I have my students learn (usually just the 1st movement).
Interesting fact: In 1781, Clementi participated in a musical contest with Mozart in Vienna, where they took turns performing and improvising at the harpsichord for the Holy Roman Emperor Joseph II. The emperor declared it a tie!