Flashback Friday: Madonna's 'Who's That Girl' Hit No. 1

AP Photo/Frank Rumpenhorst
U.S. singer Madonna on stage during her solo German performance in Frankfurt on August 23, 1987. 

'That girl' is Madonna. Duh.

"Who's that girl?" wasn't a question anyone was asking about Madonna by the time 1987 rolled around -- but it was a question on the mind of every pop lover on Aug. 22, 1987, the day that Madonna's tune "Who's That Girl," hit No. 1 on the Billboard Hot 100.

The soundtrack to the film of the same name, in which the song was featured, debuted July 21, 1987, with the film's theatrical release following on Aug. 7. The track became her sixth No. 1 single.

For today's Flashback Friday, take a look at Madonna performing the song in concert on the Who's That Girl world tour. Historical note: Madge hasn't performed the tune live since the Who's That Girl tour closed on Sept. 6, 1987.

Reminisce with us below.