Ryazhenka, or ryazhanka (Russian: ряженка; Belarusian: ражанка, Ukrainian: ряжанка),[2] is a traditional fermented milk product in Belarus, Russia, and Ukraine.

The milk is heated to a high temperature before fermentation, which is the main factor distinguishing ryazhenka, varenets, qatiq, and kaymak from yogurt-based drinks.

Historically, this was done by placing a clay pot (glechik or krinka) with milk in a traditional Ukrainian oven for a day, until it was coated with a brown crust.

Prolonged exposure to heat leads to the Maillard reaction between the milk's amino acids and sugars, resulting in the formation of melanoidin compounds that give it a creamy color and caramel flavor.

Like scalded milk, ryazhenka is free of harmful bacteria and enzymes and can be stored safely at room temperature for up to forty hours.