The loosu ponnu (Tamil: லூசு பொண்ணு; transl. 'crazy girl') is a stock character in Tamil cinema, a girl who is portrayed as attractive but naïve and unintelligent. It is regarded as the equivalent of the Manic Pixie Dream Girl and dumb blonde stereotypes in the United States. The loosu ponnu trope became increasingly popular in 1990s Tamil cinema when the masculinity of the hero became severely overblown. It has since received criticism for being misogynistic and regressive.

According to critic Baradwaj Rangan, the loosu ponnu trope emerged in an era where Tamil filmmakers began casting North Indian women, who did not know Tamil, in leading roles; due to their lip syncing not being perfect (their lines would be dubbed over by others), wild gesticulation and their emotional reactions seeming unusual, "all of this ended up making them look like mad people".

Loosu ponnus are typically depicted as being bubbly, naïve, childish, lacking professional ambition, having easily detachable ties with their families, and showing unquestioning devotion to heroic males once they fall in love with them. They are also depicted as angelic, in need of constant rescuing, and incapable of doing even simple things in life. Very often, their "cuteness" is directly proportional to how insane their actions may seem to viewers.

Known loosu ponnu characters in Tamil films are:

Besides Tamil films, loosu ponnu characters were also noted in Telugu films (known as 'pichi pilla'). Known characters in Telugu films are:

They were also noted in Kannada films with Nandini (Reeshma Nanaiah) in UI (2024).

The loosu ponnu trope has received wide criticism for being misogynistic and regressive. Actress Madonna Sebastian has expressed her dislike for it, saying, "I think it is disrespectful and when people endorse it, even heroines, it becomes a dangerous trend." Aishwarya Rajesh has consciously avoided playing such roles, citing her preference for "sensible" roles.