Two sisters are kind of upset ... because when you Google "snapchat sluts" their pictures come up, and that's only one reason they've just sued the founder.
Sarah and Elizabeth Turner claim in 2011 they were approached by Evan Spiegel, who at the time was a Stanford student and developing an iPhone App called "Picaboo."
The girls say Evan convinced them to let him shoot pictures of them playing on the beach. They say it was a free favor ... just to promote Picaboo.
They claim one of the photos was edited to make it look like Elizabeth was pulling off Sarah's bathing suit top ... and that they were nude on the beach.
Fast forward to 2014. Picaboo morphed into Snapchat -- which the sisters claim is now valued at $10 BILLION. That playful bikini pic effectively became the face of the App.
The girls are particularly pissed because Snapchat is now the premiere sexting App and they say they've been tainted by its tawdry reputation.
The women want a portion of the profits ... big money.