Welcome to the N.H.K. (Japanese: N・H・Kにようこそ!, Hepburn: N.H.K. ni Yōkoso!) is a Japanese novel written by Tatsuhiko Takimoto. It was published by Kadokawa Shoten in Japan in January 2002, and in English by Tokyopop in October 2007. The story revolves around a 22-year-old hikikomori, an asocial recluse, who gets aid from a strange girl who seems to know a lot about him, despite never having met him before. Common themes throughout the story deal with depression, anxiety, isolation, existential dread, the hardships of life and how people must deal with them in their own way. The novel profusely analyzes the hikikomori phenomenon, which is relatively widespread in Japan.

Welcome to the N.H.K. was adapted into a manga series, also written by Takimoto, with art by Kendi Oiwa. The manga was serialized between June 2004 and June 2007 in Kadokawa Shoten's manga magazine Shōnen Ace. The manga's forty chapters have been collected into eight bound volumes released in Japan and overseas. The English edition of the manga is published by Tokyopop, and the first volume was released in October 2006. The novel was also adapted into a 24-episode anime television series by Gonzo which aired in Japan between July and December 2006 on Chiba TV. In North America, the series was licensed for English release by ADV Films, who released it on DVD in 2007. In 2008, the anime became one of over 30 ADV titles acquired by Funimation.

In Japan, NHK refers to the Japan Broadcasting Corporation (Nippon Hōsō Kyōkai), Japan's national public broadcaster, but within the series the main character believes it stands for Nihon Hikikomori Kyōkai (日本引きこもり協会, The Japanese Hikikomori Association), which is a reference to the protagonist's claim of a subversive conspiracy led by NHK (the real-life broadcaster) to create hikikomori. While it mainly deals with the phenomenon of hikikomori, the plot also explores many other Japanese subcultures—for example otaku, lolicon, and Internet suicide pacts.