The Boys' Brigade is the largest Christian uniformed youth organisation in the United Kingdom and Republic of Ireland. The Boys' Brigade was founded in Glasgow, Scotland, on 4 October 1883 by Sir William Alexander Smith, and celebrated its 125th anniversary in 2008. Felden Lodge in Hemel Hempstead, Hertfordshire, no longer serves as the main headquarters as it was sold in 2023. Other regions have their own regional headquarters. Today the BB has in the region of 20,000 boys involved in over 750 companies ranging geographically from Shetland to Guernsey.
The Boys' Brigade operates in Northern Ireland and County Donegal under The Northern Ireland Boys' Brigade (BBNI) and is independent of The Boys' Brigade UK & RoI.