YJ

YJ or yJ may refer to:

Arts and entertainment:
 * Yahoo! Japan, a website
 * Young Justice, a DC comic series
 * Young Justice (TV series), TV series aired on Cartoon Network
 * Young Justice: Legacy, video games based on the TV series
 * Yakitate!! Japan, an anime
 * Weekly Young Jump, a magazine

Other uses:
 * Yoctojoule (yJ = 10−24  J), an SI unit of energy
 * Yottajoule (YJ = 1024  J), an SI unit of energy
 * Jeep Wrangler, an SUV
 * Young Judaea, a Zionist youth movement