Ter Apel (Gronings: Troapel, 8866 residents in 2004) is a town in the municipality Vlagtwedde in the northern Netherlands, in the province Groningen in the region Westerwolde. The town lies on the stream Ruiten Aa, which has the valley that together with the Ter Apeler forest belongs to the national network of nature reserves, the Ecologische Hoofdstructuur.