Technically, either
Johann Strauss the Waltz King or Richard Strauss, the more serious composer who wrote tone poems and operas. Among real musicians, though, 'Strauss' almost invariably refers to Richard Strauss. You are a total noob if you think music festivals and professional orchestras program silly waltzes all the time when you see Strauss in their repertoire.
"Hey, wanna come to my concert tonight?
The conductor's amazing, and we're playing
Strauss."
"Uhh...I don't know if I care to hear Emperor Waltz or the
Blue Danube again."
"Aww come on- we're talking 'Death and Transfiguration' here!"