What's Your Number? is a 2011 American romantic comedy film directed by Mark Mylod, starring Anna Faris and Chris Evans. Written by Gabrielle Allan and Jennifer Crittenden, the film is based on Karyn Bosnak's book 20 Times a Lady.

It was released on September 30, 2011.

In Boston, Ally Darling is a 30-something woman, struggling to make better life decisions. Her boyfriend Rick breaks up with her when she asks him to attend her sister Daisy's wedding, and she then gets laid off. On the subway home, Ally comes across a Marie Claire article entitled "What's Your Number?", which says that women who have more than 20 lovers in their lifetime have difficulty finding a husband.

After making a list of all the men she slept with, Ally realizes she's at 19, making her decide not to have sex with anyone else until she finds "the one". This lasts all of a few hours when she wakes up after Daisy's bachelorette party and discovers that she hooked up with her ex-boss Roger while drunk.

Hoping to avoid an awkward confrontation, Ally lets her musician neighbor Colin Shea into her apartment so that Roger will leave. It turns out that Colin was only over to avoid a girl he just slept with, because he doesn't want to give the women he sees any expectations.

Ally then runs into "Disgusting Donald", her once overweight ex-boyfriend, now successful and attractive, with his fiancée. She decides to track down all her exes hoping that one will have grown into the man she wants to marry, and therefore the number of men she has slept with won't ever increase. Ally gets help from Colin, who is skilled in "digging up dirt", to find all her exes in exchange for letting him come to her place after his one-night stands. She asks Colin to pay particular attention to one ex, Jake Adams, who Ally sees as "the one that got away".

Things do not quite work as Ally hoped and, one-by-one, she remembers why it didn't work out with each. It ranged from one being in the same job since their break-up to another requiring her to pretend to be British. Depressed after the failed meetings, Ally has a night out with Colin culminating in their growing closer and almost having sex. She stops him, but decides to take him as her date to Daisy's wedding.

Daisy and Ally's friends worry she is falling for him, warning and reminding her of his promiscuous nature. She is later infuriated to find out Colin had found Jake Adams' contact details but withheld them, believing they were going to become an item, and they have a falling-out.