Lomnice nad Popelkou is a town situated in the Semily District within the Liberec Region of the Czech Republic. It lies on the border between the Giant Mountains Foothills and the Ještěd–Kozákov Ridge, positioned along the Popelka Stream. The Cidlina River originates in the southern part of its municipal territory, while the highest point is the mountain Tábor at 678 meters above sea level. Geographically, it is located approximately 33 kilometres southeast of Liberec.

The area was colonized at the turn of the 12th and 13th centuries due to harsh climatic conditions, with the first written mention appearing in the Chronicle of Dalimil between 1308 and 1314. Ownership shifted among various families, including the Waldsteins and the Counts of Morzin, before reaching its greatest prosperity under the Waldstein family from 1524 to 1654. The Thirty Years' War halted development, after which the estate passed through several aristocratic owners until the Counts of Rohan.

The historic town centre is well preserved and protected as an urban monument zone, centered around Husovo náměstí. Key landmarks include a neo-Gothic town hall from 1864, Lomnice nad Popelkou Castle in its Baroque form, and the Church of Saint Nicholas. The locality of Karlov, founded in 1739–1740, is protected as a village monument reservation known for its preserved half-timbered houses representing local vernacular architecture.

Cultural life is supported by the Town Museum and Art Gallery, located in the Neoclassical Hrubý dům building from the 1820s. The town is also recognized for its ski club, LSK Lomnice nad Popelkou, founded in 1925, which has produced notable ski jumpers such as Roman Koudelka and Čestmír Kožíšek. The area attracts visitors interested in its preserved historic architecture and its connection to winter sports traditions.

The population is recorded at 5,626 as of 2025. The largest employer is the Samohýl group a.s., which deals in veterinary drugs and pet products. Transport infrastructure includes railway lines starting from the town toward Městec Králové and Stará Paka. The name derives from the local stream, originally called Lomnice, linked to the Czech adjective lomný meaning noisy or crooked.