Mierzwice-Kolonia [mjɛʐˈvit͡sɛ kɔˈlɔɲa] is a village in the administrative district of Gmina Sarnaki, within Łosice County, Masovian Voivodeship, in east-central Poland.

There was a resort of Polish State Railways here, now privately owned.

In the village is located the railway line between Siedlce and Czeremcha.

Under this common name of village it is known for holidaymakers and is popular as a Fronołów more than Mierzwice-Kolonia.

Fronołów name probably comes from the surname of Russian engineer - Fronolov who designed the steel railway bridge at this location.