The British Columbia Junior Tier 1 Lacrosse League, or BCJT1LL is a Junior B box lacrosse league based in the Lower Mainland of British Columbia, Canada, sanctioned by the British Columbia Lacrosse Association. The league champion competes for the British Columbia Junior B Provincial Championship. Teams have competed for the Founders Cup, a national tournament which determines the Canadian Junior B lacrosse champion.
The league was known as the BC Intermediate A League until the end of 2017. At the beginning of the 2018 season, 17 & 18 year old lacrosse was merged with Junior B, expanding the bracket to the age brackets used by the rest of the Canadian Lacrosse Association.
Since 2018, the BCJT1LL champions have played a provincial championship series against the TOJLL winners. The T1 champion has won every series.