IRON MAIDEN singer BRUCE DICKINSON spotted a "fan" texting through their show in Indianapolis last Thursday night . . . and called him out on it.

(CAREFUL) --As they were starting to play "Wasted Years", Bruce shouted, quote, "Oh, for [eff's] sake, the man with the bald head in the white shirt, you've been texting for the last [effin'] three songs!  You're a wanker!"

You can find the video by clicking HERE.  Bruce rips into the fan 14 seconds in.  WARNING:  This video is UNCENSORED . . . and AWESOME!