B
- Baleally Stream, County Dublin
- Ballinascorney Stream, County Dublin
- Ballinderry*
- Ballinglen River, County Mayo
- Ballintotty River, North Tipperary
- Ballyboughal River, County Dublin
- Ballycassidy*
- Ballyfinboy River
- Ballymaice Stream, County Dublin
- Ballymeeny River, County Sligo
- Ballynahatty*
- Ballynahinch*
- Ballyogan Stream, County Dublin
- Balsaggart Stream, County Dublin
- Bandon
- Bann (Wexford)
- Bann* — longest river in Northern Ireland. Upper Bann flows into Lough Neagh and then continues north as the Lower Bann.
- Bannagh*
- Barrow
- Bartramstown River, County Dublin
- Belderg River, County Mayo
- Bellanaminnaun River, County Mayo
- Bellawaddy River, County Sligo
- Black River, County Mayo
- Blackbanks Stream, County Dublin
- Blackditch Stream, County Dublin
- Blackwater, Kerry
- Blackwater, Cavan and Meath
- Blackwater, Kildare and Meath
- Blackwater, Munster
- Blackwater, Ulster*
- Bloody Stream, County Dublin
- Boggeen Stream, County Dublin
- Boherboy Stream, County Dublin
- Boyle, County Roscommon
- Boyne
- Bracken River, County Dublin
- Bracken, Balbriggan
- River Bradoge, County Dublin
- Bride
- Bride's Glen Stream, County Dublin
- Bride's Stream, County Dublin
- Broad Meadow River, County Dublin
- Brockey Stream, County Dublin
- Broghane Stream, County Kerry
- Brook Stream, County Dublin
- Brosna
- Brownsbarn Stream, County Dublin
- Burntollet*
- Bush*
Read more about this topic: Rivers Of Northern Ireland