Did Beethoven write a piece of music including theme and variation?

Yes, Beethoven wrote several pieces of music that include a theme and variation. One notable example is his "Symphony No. 9 in D minor, Op. 125," which features a theme and variations in its fourth movement. The theme is a simple melody that is introduced in the first section of the movement and is then repeated in different forms throughout the movement. The variations are elaborate and often quite different from the original theme, but they all share the same underlying melody. This piece of music demonstrates Beethoven's mastery of the theme and variation form and is considered a masterpiece of classical music.