Jean-Baptiste le Rond d'Alembert (November 16, 1717 – October 29, 1783) is a French mathematician, mechanician, physicist, philosopher, and music theorist.

Until 1759 he is also co-editor with Denis Diderot of the Encyclopédie.

D'Alembert's formula for obtaining solutions to the wave equation is named after him; the wave equation is sometimes referred to as d'Alembert's equation.