The Bert Diaries are a series of novels written in the form of a diary, by Swedish writers Anders Jacobsson and Sören Olsson. The main character is a Swedish teenager called Bert Ljung, living in Öreskoga, a fictional town in Sweden, in the late 1980s and early 1990s. The first book came out in 1987. Bert and his friends also have a pop/rock band, the Heman Hunters.

A TV series was made in 1994, directed by Tomas Alfredson and Svante Kettner. It was followed by a feature film in 1995, also directed by Alfredson. In late-July 2016 the filming of a new Bert film was announced.

Between 1993 and 2002, a comic book, FF med Bert, was published and between 1992 and 1999, comic albums were published.

Bert Ljung is the main character, the only son of optician Fredrik Ljung and bus driver Madelene (née Olsson). Bert starts as a 12-year-old child in the spring term of the 5th grade but later becomes a mischievous teenager discovering his own sexuality. From the book Berts första betraktelser, the readers can learn that Bert Ljung was born on February 21, 1976, but there are a lot of anachronisms, with the later books largely following a floating timeline. His family is also depicted in the books. In Berts bryderier, Bert tells the tale of his paternal great-grandfather Vladimir Livanov, who hailed from Saint Petersburg and made glasses, before building a raft and paddling with his hands and ending up in Gotland, where he married Beda (who dies on October 14 in Berts bravader). They had a son - Bert's paternal grandfather Stanislav Livanov, who after being teased for his name, changed his name at 18 to Sten Ljung. He married Märta Öberg, and they had two sons - Fredrik, and his younger brother Janne, who became a successful businessman in New York City. Janne visits Bert and his family over Christmas in Berts ytterligare betraktelser and again in Berts befrielse, and Bert visits him in NYC with family in Berts vidare betraktelser and on his own in Bert Babyface. His religious maternal grandmother Svea Olsson also makes a lot of appearances in the books. Bert plays the electric bass, sings and writes songs in the amateur rock band Heman Hunters (changed to Population Station Groovy WY in Berts befrielse and after a mistake made with posters, to 13 kor och en spann (13 Cows and a Bucket in Swedish) in Bert och beundrarinnorna). He also plays soccer for the amateur team Öreskoga-Kamraternas Idrottsförening, before quitting in Bert och beundrarinnorna. Bert is also interested in mopeds, which in Sweden, one is allowed to drive at 15. He gets a Crescent Trampis moped in Berts bekännelser, before selling it in Berts befrielse.

Åke Nordin is Bert's best friend. His mother died in cancer when he was 7 years old. While Bert is interested in girls, Åke is more interested in science, carrying out dangerous experiments with chemicals on his little sister Doris. Åke is the Heman Hunters' electrician and overall technician.

Torleif comes from a family depicted as "intellectual". Torleif likes classical music, and plays the flute and the keyboards in the Heman Hunters. He moves to Helsingborg at in January in Berts bekännelser, but makes a brief return a few days later. Bert, Åke and Erik meet him again in Helsingborg in Berts bokslut.

Lill-Erik is the weak guy. He plays the accordion or the drums in the Heman Hunters. Before his arrival from Sundsvall, rumors make everybody think he is the strong "Stor-Erik" or "Erik the Great" who is able to beat up Klimpen. He has a fear of girls, after he showed his penis to his cousin at 5 years old and she told him it looked like a worm. Despite that, he had been on dates in later books.

Rebecka Molin is the first girl Bert is in love with, which occurs in the mid 5th grade when the book series start.