Bangkok Symphony Orchestra, Thailand

Beecham Symphony Orchestra, St. Helens, Lancashire, England

Several symphony orchestras:

Black September Organization, Palestinian militant group

Basic Security Option, an option for IP datagrams defined in RFC 1108

Broad System of Ordering, an indexing system

BSO is a three letter acronym which may stand for:

Brake Standard Open, a designation of British railway carriage

The Brian Setzer Orchestra, a popular band of the late 1990s swing revival

Österreichische Bundessportorganisation, the Austrian Federal Sports Organization

Baltimore Symphony Orchestra, Baltimore, Maryland, U.S.A.

Bloomington Symphony Orchestra, Bloomington, Indiana, U.S.A.

Boston Symphony Orchestra, Boston, Massachusetts, U.S.A.

Bournemouth Symphony Orchestra, Bournemouth, Dorset, U.K.

Baloch Students Organization, Balochistan.

British School of Osteopathy, the UK's oldest osteopathic institution

Broward Sheriff's Office of Broward County, Florida, USA

BSO, a European IT company founded by Eckart Wintzen, now a part of Atos Origin.