Comarnic (Romanian pronunciation: [koˈmarnik]) is a town in Prahova County, Muntenia, Romania, with a population of 11,106 as of 2021.

Four villages are administered by the town: Ghioșești, Podu Lung, Poiana, and Posada.

It lies towards the southern end of the Prahova Valley, along the Prahova River, in the main on the left bank, but with some of the component villages on the right bank of the river.

It is crossed by national road DN1 (part of European route E60), which starts in Bucharest and goes north towards Brașov and on to the border with Hungary near Oradea; the partially built A3 motorway will also go through the town.

The Comarnic train station and the Posada halt serve the CFR Main Line 300, which runs parallel to DN1.