S/2003 J 1, a former name for Eukelade, a retrograde irregular satellite of Jupiter
J1 Live Concert DVD, a DVD release by Chinese singer Jolin Tsai
J1 denotes the Personnel, or Human Resources function of a U.S. Joint Command (for example: the J-1 Directorate in Special Operations Command Europe refers to the Human Resources Directorate)
First-order Bessel function of the first kind, <math>j_1</math>