Black Lagoon (ブラック・ラグーン Burakku Ragūn), commonly styled in caps as BLACK LAGOON, is a Japanese manga series written and illustrated by Rei Hiroe. It has been published in Shogakukan's Monthly Sunday Gene-X since 2002, and thirteen collected volumes have been released so far as of December 2023. It was later adapted by Madhouse into an anime television series that aired from April to June 2006 for twelve episodes. A second season, subtitled The Second Barrage, ran for twelve weeks starting on October 2, 2006. A five volume original video animation series, titled Roberta's Blood Trail, was released from July 2010 to June 2011.

Viz Media began releasing an English translation of the manga in North America on August 12, 2008. Madman Entertainment licensed the anime in Australia and the United Kingdom. The anime was dubbed and originally licensed in English by Geneon Universal Entertainment, now licensed by Funimation Entertainment, in North America. Funimation later licensed the OVA, which also was licensed by Kazé in the UK, for release in Spring 2013.

The story follows a team of pirates/mercenaries known as Lagoon Company, which smuggles goods in and around the seas of Southeast Asia, with the story beginning in 1995. Their base of operations is located in the fictional harbor city of Roanapur in southeast Thailand. They transport goods in the 80-foot (24 m) Elco-type PT boat Black Lagoon. Lagoon Company does business with various clients, but has a particularly friendly relationship with the Russian crime syndicate Hotel Moscow. The team takes on a variety of missions—which may involve violent firefights, hand-to-hand combat, and nautical battles—in various Southeast Asian locations such as Isabela, Basilan in the Philippines, Pangkalpinang in Indonesia, and an attempted trip to Phú Quốc Island in Vietnam. When not doing much, the members of the Lagoon Company spend much of their down time at the Yellow Flag, a bar in Roanapur which is often destroyed in firefights.

In an interview with Otaku USA, Rei Hiroe stated that Black Lagoon was inspired by James Ellroy, John Woo, Quentin Tarantino and Stephen King, as well as hearing about actual piracy cases in the East China Sea in the 1990s.

Black Lagoon includes a considerable amount of graphic violence, often involving violent gun fights and spectacular physical feats in battle. Many of the characters who are most skilled with weapons (mainly guns) are women, thereby bearing a similarity with "girls-with-guns" genre with many of the women adhering to a gun-girl stereotype. Some of the scenes and dialogue are within the realm of dark comedy, as humorous moments occur or are mentioned during and after many violent battles.

The character concept, gritty atmosphere and violence blending with black comedy depicted in Black Lagoon pays a homage to the films by Quentin Tarantino and the Coen Brothers. The Yellow Flag bar and standoff scenes in the series pay a tribute to spaghetti westerns; Tarantino is known for making references to spaghetti westerns in his films. It also make references to Tarantino's favorite films, such as The Wild Bunch poster (titled The Wild Punch) seen in Revy's bedroom in Episode 11 of the anime and Revy mentioning My Bloody Valentine in Episode 23 (Chapter 34).

The "Fujiyama Gangsta Paradise" arc showed that most of the characters throughout the series actually speak English, with the Japanese simply being done for the audience. While the English voice acting in the anime is heavy in Japanese pronunciation, nearly all occurrences of English lines in the manga are accurate. Some English misspellings in the series are for parody purposes, such as misspelling a celebrity name, movie poster, or a cigarette brand. Likewise, instances of Cyrillic Russian script are also all accurate with just a few mistakes in the series, such as the following: the Russian adverb "больше" is misspelled as "бопьше" in Chapter 00; the abbreviation "внешторг" is misspelled with a "щ" as "внещторг" in Chapter 52; Episodes 23 and 24 of the anime show the boat Marya Zaleska (Мария Залеска) with the last name Zaleska misspelled as "Зейрска"; the infinitive "занять" is misspelled with a hard sign (ъ) as "занятъ" in Chapter 68; there is a character called Zachamin which should be "Zamyatin" since the two kana "mi" and "chi" were switched; and the typo "за встрчу" instead of "за встречу" in Chapter 110.

Written and illustrated by Rei Hiroe, Black Lagoon premiered in Monthly Sunday Gene-X on April 19, 2002. Chapters run monthly and are later collected into tankōbon volumes by Shogakukan. The first was released on December 12, 2002, and to date thirteen volumes have been published. After having been on hiatus since mid-2010, the series resumed in the February 2013 issue of Monthly Sunday Gene-X and is currently ongoing.

The manga was licensed for an English-language release in North America by Viz Media. The first volume was released on August 12, 2008. Madman Entertainment distributes Viz's release of the series in the United Kingdom. Black Lagoon has also received domestic releases in many other countries; in France, Germany, Hong Kong, Italy, Singapore, South Korea, Spain, Mexico, Poland, Finland and Turkey, by Kabuto, Carlsen Comics, Jade Dynasty, Panini Comics, Chuang Yi, Haksan Publishing, Norma Editorial, Grupo Editorial Vid, Waneko, Punainen jättiläinen and Athica Yayınları respectively.

An anime adaptation of Black Lagoon, produced by Madhouse, aired on Chiba TV from April 8, 2006 to June 24, 2006 for twelve episodes. A second season, labeled Black Lagoon: The Second Barrage and consisting of twelve more episodes, ran from October 3, 2006 to December 19, 2006. The second season focuses less on character development than the first season and more on the jobs they do. A five volume original video animation titled Black Lagoon: Roberta's Blood Trail was released in July 2010.

The anime was licensed in the United Kingdom and Australasia by Madman Entertainment. On July 3, 2008, Geneon Entertainment and Funimation Entertainment announced an agreement to distribute select titles in North America. While Geneon will still retain the license, Funimation will assume exclusive rights to the manufacturing, marketing, sales and distribution of select titles. Black Lagoon was one of several titles involved in the deal. Geneon's English dub premiered on G4 Canada on October 26, 2007 and Starz Edge began airing it on February 29, 2008 to American audiences. The series aired in Australia on the Sci Fi Channel.

The first season was released on six DVDs, each containing two episodes, between August and December 2006. The second season mirrored this, being released from January to June 2007. The Blu-ray Disc releases of the two seasons included a total of seven short omake specials, each no longer than five minutes, that depict the characters in various humorous situations. In 2010, the series was released in four, two for each season, boxsets from August to September.

Geneon's North American dub was released on three DVD compilations, each containing four episodes, between May 22 and September 18, 2007. After being released individually, with volume one having a limited edition version containing a steelbook box that comes with a bonus disc with slots for all 3 volumes, the boxset of the entire first season was released December 30, 2008. The fourth bonus disc, available in the season one box set or the volume one steelbook edition, has a 15 minute behind the scenes with the English crew and voice actors, the "Red Fraction" music video performed by Mell, promotional videos, the creditless opening and ending, and Japanese opening. The Second Barrage volumes were released in the same manner, with the box set released in North America on April 14, 2009, case with episodes 13–24 on three discs with English/Japanese audio and English subtitles. The box set/steelbook version bonus disc includes promotional videos and the creditless opening and ending. At Anime Expo 2010, Funimation announced their licensing of the Roberta's Blood Trail OVA, which was released in 2013. The first and second seasons were re-released on Blu-ray Disc/DVD combo pack on December 4, 2012.

The series returned to American television on the Funimation Channel on February 15, 2013. The anime has also aired in Italy on MTV Italy, in Sweden on ZTV and on Animax in Spain, Portugal and Germany.

The Black Lagoon series has also spawned two official spinoff series in recent years, both of which have ongoing serialization in Sunday GX. The first spinoff series is Dismemberment Galore! The Gore Gore Girl starring Frederica Sawyer as the main protagonist, which is authored and illustrated by Tatsuhiko Ida with manuscript supervision and original characters by Rei Hiroe; it was first serialized in September 2019 and currently has nine volumes as of January 2025. The second spinoff series is Eda Initial Stage starring Eda as the main protagonist, which is authored and illustrated by Hajime Yamamura with original characters by Rei Hiroe; it was first serialized in April 2022 and currently has six volumes as of February 2025. Besides being published in Japanese by Shogakukan, Eda Initial Stage is also officially published in Taiwanese Mandarin by Ever Glory Publishing.

There are two Black Lagoon light novels both written by Gen Urobuchi with illustrations by Rei Hiroe. The first light novel, Shaitane Badi, was published on July 18, 2008, and the second light novel, Ballad of the Sinful Wizard, was published on January 18, 2011. Additionally, there are a few official art books featuring illustrations of Black Lagoon characters & subjects, including Barrage — Rei Hiroe Artworks (2007), Call Mission — Rei Hiroe Artworks 2 (2014), and the 20th anniversary art book Onslaught: BLACK LAGOON Illustrations (2021). For the anime, in April 2007 Madhouse released a book containing many settei under the ISBN 4961524347445. In December 2023, an online action role-playing game, Black Lagoon: Heaven's Shot, was released for desktop and mobile in Japanese, English, Korean, and Traditional Chinese. It is a free-to-play game monetized through gacha game mechanics.

As of October 2007, the manga series has sold over 3 million copies in Japan, and over 8.5 million copies in circulation by January 2022. About.com's Deb Aoki listed Viz Media's English release of Black Lagoon as the best new seinen manga of 2008, along with Gantz. The anime series has received internationally positive reviews. Chris Beveridge of Anime on DVD goes so far as to say: "To my surprise, knowing practically nothing about the show beyond a two minute clip at a convention, Black Lagoon manages to kick all kinds of ass. In English no less. The draw of a full bitrate 5.1 mix got me to watch it in English only to find that with most of the characters being western and in settings outside of Japan it works very well."