Sandra Ann Lauer, later Sandra Cretu, commonly known mononymously as Sandra, is a German pop singer who enjoyed mainstream popularity in the 1980s and early 1990s with a string of European hit singles, produced by her then-husband and musical partner, Michael Cretu, most notably "(I'll Never Be) Maria Magdalena" (1985), "In the Heat of the Night" (1985), "Everlasting Love" (1987), "Secret Land" (1988), "Hiroshima" (1990), and "Don't Be Aggressive" (1992). Her albums Into a Secret Land (1988) and Close to Seven (1992) have won Sandra high critical acclaim.

"Hi! Hi! Hi!" is a 1986 song performed by German pop singer Sandra. It was written by Michael Cretu, Hubert Kemmler and Klaus Hirschburger, and produced by Cretu and Armand Volker.