Sienno is an urban-rural municipality located in the Masovian Voivodeship, within Lipsko County, with its administrative seat in the town of Sienno. Historically, between 1975 and 1998, the municipality was part of the Radom Voivodeship. From a historical perspective, during the time of the Kingdom of Poland, the municipality belonged to the Iłża County in the Radom Governorate. In 1870, the territory of the abolished town of Sienno was incorporated into the municipality, which significantly influenced its borders and historical development.
The municipality covers an area of 147.15 km², of which 80% is agricultural land and 17% is forested. Sienno constitutes 19.68% of the total area of Lipsko County. According to demographic data, at the end of 2012, Sienno had a population of 6,098. The municipality includes numerous villages, such as Adamów, Bronisławów, Janów, Olechów, and Wierzchowiska, reflecting its diverse and dynamic settlement structure.
Sienno borders municipalities such as Bałtów, Bodzechów, Brody, Ciepielów, Kunów, Lipsko, Rzeczniów, and Tarłów, underscoring its local significance. It is also worth noting that Sienno boasts rich cultural traditions, manifested in local customs, rituals, and festivals. The municipality is a place where history intertwines with the daily lives of its residents, and the local community actively cherishes its cultural heritage.