Johannes Voorhout was a Dutch Golden Age painter.

Voorhout was the son of the Amsterdam clock maker Cornelis Voorhout. Seeing that his son was better suited to drawing than the technical aspects of watch making, he apprenticed him to Constantijn Verhout in Gouda. This Verhout was a painter of modern history scenes, and after 6 years, he moved back to Amsterdam in 1664 to work in the workshop of Jan van Noordt, a history and portrait painter. After working there for 5 years, he married in 1670, and in 1672, worried about a pending invasion by the French, he fled the country and settled in Friedrichstadt, where his wife had some friends, and he was received by Juriaan Ovens. Ovens wanted him to come work for him, but Voorhout turned down his offer, but followed his advice to try his luck in Hamburg. There he was quite successful, and that is where his son Johannes was born in 1677.

For Dirck Clant of Groningen, the lord of the Castle Hanckema, Voorhout painted a large portrait of the Stadthouder William III on horseback for him, that was later placed in his castle near Groningen as an over-the-mantel piece. This portrait is now in the Groninger Museum and was later used in the 1930s as a model for the Dutch 500 guilder note.

Having heard that the politics of Amsterdam were back to normal, he returned there in 1677, where he started his own workshop. He taught his son Johannes II, and Ernst Stuven, but never had the success that he had enjoyed in Hamburg. This was partially because he was so productive, that customers couldn't make a choice when they came to his studio, but also it was a result of the market in Amsterdam being much more competitive than in Hamburg, due to the high number of competent painters there. Houbraken ends his biographical sketch of him with the comment that he was perhaps too focused on painting itself; and spent too little time on commercial interests such as flattery and deception.