Widely cited as one of the most influential figures in the early cloud rap era, Yung Lean rose to prominence in 2013 with his song "Ginseng Strip 2002", which went viral on YouTube.

He released the albums Nectar (2019), Blodhundar & Lullabies (2020) and Sugar World (2023) under the pseudonym Jonatan Leandoer96, a project which strays away from his hip-hop roots and goes for a blend of indie rock and neofolk.

Håstad was born on 18 July 1996 in Stockholm, Sweden,[5] to Kristoffer Leandoer [sv], a Swedish poet, fantasy author, and translator of French literature who owned a book publishing company[6] and Elsa Håstad [sv], a former human rights activist who worked with LGBT groups in Russia, Vietnam, and South America,[7] serving as the Swedish ambassador to Albania from 2019 to 2023.

[9] Håstad began to develop an interest in hip hop music, mentioning 50 Cent's Get Rich or Die Tryin', The Latin Kings's Mitt Kvarter and Nas's Illmatic as his early influences.

[10][11][12] In 2012, Håstad met Yung Sherman and Gud in a local Stockholm park and they struck up a friendship, discovering they enjoyed much of the same music, going on to form the collective Hasch Boys.

Consequence of Sound placed "Ginseng Strip 2002" at number 44 on their "Top 50 Songs of 2013",[24] while Vibe included Unknown Death 2002 in their list, "The 10 Most Overlooked Debut Rap Mixtapes of 2013", describing it as "a natural progression from the freely associative, often nonsensical rhymes of Lil' B with a keener sense of melody".

Later that same year, Acclaim Magazine had Yung Lean as their guest for a Q&A "smalltalk" segment, where they asked him about a wide variety of miscellaneous things, including his favourite hangover cure and his desktop wallpaper.

[31][38][39] The album was accompanied with North American and European tours, beginning on 1 December in New York with a nearly sold-out show on Webster Hall's main ballroom stage.

[45] On 14 December 2016 he released the mixtape Frost God containing eight tracks including "Hennessy & Sailor Moon" and "Crystal City" which featured A$AP Ferg.

Håstad released his third studio album Stranger on 10 November 2017, with the singles "Red Bottom Sky", "Hunting My Own Skin", and "Skimask", through Stockholm label YEAR0001.

In an interview with Complex in January 2018, Håstad announced he was writing several film scripts, including one based around Swedish serial killer John Ausonius, best known as "The Laser Man".

[46] In February 2018, Yung Lean released the single "King Cobra" with Thaiboy Digital, as well as a collaboration with Converse that consisted of a shoe and several items of clothing titled "One Star Toxic".

On 8 April 2022, Yung Lean released a 12-track mixtape titled "Stardust" containing features from FKA twigs, Skrillex, Drain Gang and Ant Wan.

[52] On 14 December 2022, the single "Blue Light" was released as Jonatan Leandoer96, accompanied by a music video directed by Olle Knutson and Philip Hovensjö.

[56][57] On 4 November 2024, it was announced that Yung Lean would appear alongside Charli XCX in the upcoming film Sacrifice, marking his feature-film debut.

[21] Fact magazine viewed the Unknown Death 2002 mixtape as "a logical continuation of Clams Casino and Beautiful Lou's innovative techniques, emerging with thick, melancholy numbers that drip with a rare and earnest allure.

Outside of music, Håstad is writing a screenplay about a "strange gangster drama" and a rock opera about John Ausonius, a Swedish serial killer.

[77][78][79] In 2019, Yung Lean was awarded the Bram Stoker Medal of Cultural Achievement by the University Philosophical Society at Trinity College, Dublin.