18 in D major, K. 576, was composed by Wolfgang Amadeus Mozart as part of a set of six for Princess Frederica Charlotte of Prussia in 1789.

In a letter to a fellow Freemason Michael von Puchberg, dated 12 July 1789, Mozart wrote "meanwhile I am working on six easy piano sonatas for Princess Friederike and six quartets for the King".

Charles Rosen offered a moderate viewpoint, considering that Mozart may have mistakenly believed that these passages were easy (as they are in two parts, one in each hand), even if they are not actually so in practice.

The development section includes many different keys, but starts in the dominant, using counterpoint and harmonic imbalance and exploration.

[1] The last movement has a playful mood and is light in texture, however the articulation is marked carefully and precisely to maintain clarity, as was common of the time.