20th Century Girl (Korean: 20세기 소녀; RR: 20segi Sonyeo) is a South Korean coming-of-age romance drama film written and directed by Bang Woo-ri in her feature film debut, starring Kim Yoo-jung, Byeon Woo-seok, Park Jung-woo, and Roh Yoon-seo.

[2] Set in 1999, the story revolves around Na Bo-ra (Kim Yoo-jung), a seventeen-year-old high school student with a bright personality.

Bo-ra's best friend, Yeon-du (Roh Yoon-seo), who has been preparing to visit the US for heart surgery, suddenly declares that she cannot leave as she has fallen in love with a boy from their school whose name she knows as Baek Hyun-jin (Park Jung-woo).

When Yeon-du returns to Korea after successful heart surgery, they realize that Bo-ra has been following the wrong boy, and that the real 'Baek Hyun-jin' whom Yeon-du loves is actually Poong Woon-ho, a confusion caused by the boy wearing his friend's school jacket bearing his name tag.

On the day of his departure, with the help of Yeon-du and Hyun-jin, Bo-ra arrives at the train station just in time for them to confess their feelings before separating.

[22] Within three days of its release, it debuted at 2 on Netflix's global chart of Top 10 non-English movie category for the week of October 17 to 23, with eight million hours viewed.

Lee concluded, "Though its potential is not fully realized, '20th Century Girl' does manage to add to the timeworn theme of first love by providing a moving examination of what makes certain moments and certain people unforgettable.

"[24] In his review in South China Morning Post, James Marsh praised the performance of Kim Yoo-jung as a "dazzling central turn," and described the movie as a "genuinely heartwarming comedy of youthful errors."