The Boys' Brigade (BB) is an international interdenominational Christian youth organisation, conceived by the Scottish businessman Sir William Alexander Smith to combine drill and fun activities with Christian values. Following its inception in Glasgow in 1883 the BB quickly spread across the United Kingdom, becoming a worldwide organisation by the early 1890s. As of 2018, the Boys' Brigade claimed 750,000 members in 60 countries.

Sir William Alexander Smith, the founder of the Boys' Brigade, was born in Pennyland House, Thurso, Scotland. He was the eldest son of Major David Smith and his wife Harriet. He had one sister and two brothers.