The study was conducted by Badoo.com, a social networking platform for meeting new people. It gave its female users across Britain, US, Canada, Australia and New Zealand, the chance to pick from a shortlist of 10 "ice-breakers", which women could use to open an online conversation with other Badoo users.
Hepburn's line, delivered by the actress to Cary Grant in the 1963 romantic thriller "Charade", emerged the most favourite when it came to women approaching men.
"This is a study of chat-up lines in action, and not just any lines, but Hollywood's finest," Louise Thompson, Badoo's director of public relations, said in a statement.
The list consisted of 10 chat-up lines - flirtatious or romantic lines - first delivered by actresses in Hollywood movies. Badoo then analysed the data from 1,000 interactions using such lines. It measured which lines were most sent by women.
Top five chat-up lines most picked by women to approach men:
1. "I don't bite, you know, unless it's called for." - Audrey Hepburn to Cary Grant in "Charade" (1963)
2. "You don't have to say anything! Oh, maybe just whistle. You know how to whistle don't you?" - Lauren Bacall to Humphrey Bogart in "To Have and To Have Not" (1944)
3. "You don't know how hard it is being a woman looking the way I do." - Kathleen Turner to Bob Hoskins in "Who Framed Roger Rabbit?" (1988)
4. "Was that cannon fire, or is it my heart pounding?" - Ingrid Bergman to Humphrey Bogart in "Casablanca" (1942)
5. "You give me premature ventricular contractions! You make my heart skip a beat." - Natalie Portman to Ashton Kutcher in "No Strings Attached" (2011)