Håstad was born on 18 July 1996, in Minsk, Belarus to Kristoffer Leandoer, a Swedish poet, fantasy author, and translator of French literature who owned a book publishing company and Elsa Håstad, who is a human rights activist working with LGBT groups in Russia, Vietnam, and South America. Håstad spent his early childhood in Minsk, Belarus, where his mother moved the family so Håstad could have a similar childhood to her. His maternal grandfather was British playwright Arnold Wesker.
They returned to Sweden and settled in Stockholm when Håstad was somewhere between the ages of three and five. He was raised in the city's Södermalm district. Håstad grew up speaking both Russian and Swedish. During his time in high school, Håstad often got in trouble for doing drugs or writing graffiti. He also had a job at a local McDonald's. When he was 15, he was put on probation for smoking cannabis. In his youth, he began to develop an interest in hip hop music, mentioning Get Rich or Die Tryin' by 50 Cent, Mitt Kvarter by Swedish hip-hop group The Latin Kings and Illmatic by Nas as his early influences.
2012–2013: Career beginnings, Lavender and Unknown Death 2002
In 2012, Håstad met Yung Sherman and Yung Gud in a local Stockholm park and they struck up a friendship, discovering they enjoyed much of the same music. Together with several other mutual friends they formed a group known as Hasch Boys. Another group of Stockholm artists who would later form the group Drain Gang were also members of Hasch Boys. Drain Gang members are friends of Yung Lean and they frequently collaborate together.
When many of the other members of Hasch Boys began to lose interest in the group, Håstad, Sherman and Gud broke off and formed the group Sad Boys as a trio. By 2012, Yung Gud and Yung Sherman were producing and mixing music while Håstad had begun writing lyrics and recording vocals in a makeshift studio in his basement. They shared the music they made on the platform SoundCloud and Tumblr, where Lean began to generate a large following. Sad Boys performed their first show in Gothenburg, Sweden on 5 May 2013.
Yung Lean became widely known when the music video for his track "Ginseng Strip 2002" went viral, exceeding 24 million views on YouTube as of July 2019. That same year, he put out his first official releases: Unknown Death 2002 and an EP titled Lavender which includes the track "Ginseng Strip 2002" along with other songs that were cut from Unknown Death 2002. Consequence of Sound placed "Ginseng Strip 2002" at number 44 on their "Top 50 Songs of 2013", 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".
In 2013, Yung Lean and Sad Boys toured throughout Europe. 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.
2014–2016: Unknown Memory and Warlord
In 2014, Yung Lean and Sad Boys embarked on the White Marble Tour, playing in 24 cities across Europe. Shortly after the conclusion of this tour Sad Boys announced a further Black Marble Tour, which would include several performances in cities across North America. The first of these shows took place in July at the Webster Hall in New York City, and was well received by writers for publications such as XXL, and The New York Times.
Yung Lean starred on Studio PSL in May 2014 and was also one of five final nominees for the 2014 [P3 Guld in the Hip Hop/Soul category.
Yung Lean released his debut full-length album, titled Unknown Memory on 23 September 2014. 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.
Yung Lean released his second full-length album, Warlord, on 25 February 2016; he also released a line of clothing, "Sad Boys Entertainment". Håstad modelled for Calvin Klein's July 2016, AW16 Campaign. During his Warlord American tour, his tour bus in Pennsylvania was shot at. Håstad was also featured on critically acclaimed Blonde by Frank Ocean where he provided backup vocals on the songs "Godspeed" and "Self Control". According to Håstad, his part on the project was recorded when he was seventeen in Ocean's apartment in London.
Yung Lean released a surprise track on 25 November 2016 titled "Hennessy & Sailor Moon (feat. Bladee)". 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.
2017–present: Stranger and Poison Ivy
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. 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 2 November 2018, Håstad released his fourth studio album Poison Ivy with the single "Happy Feet" released on 24 October 2018. The album, a collaboration with Whitearmor, a member of group Drain Gang whom Håstad frequently collaborates with, debuted at number 44 on the Sweden Albums Charts, the Sverigetopplistan.
In 2019, Yung Lean was awarded the Bram Stoker Medal of Cultural Achievement by the University Philosophical Society at Trinity College, Dublin.
Outside of music, Håstad is writing a screenplay about a "a strange gangster drama" and a rock opera about John Ausonius, a Swedish serial killer. Håstad has aspirations to become an actor.
Håstad has several hobbies, including reading, ceramics, painting and playing piano. Håstad began to pick up painting following his release from a mental health hospital as a way to relax.
While recording his second studio album Warlord, Håstad lived in Miami Beach, Florida. During this time, Håstad became addicted to Xanax, lean and cocaine. On 7 April 2015, Håstad overdosed and was hospitalized in Mount Sinai Medical Center & Miami Heart Institute. Håstad's overdose and subsequent hospitalization coincided with the tragic death of his manager and close personal friend, Barron Machatt. After the incident, Håstad moved back to Sweden to live with his family.
- 2015: New Era
Död Mark (punk band with Yung Gud)
- 2016: Drabbad av sjukdom
Jonatan Leandoer127 (renamed to Jonatan Leandoer96)
- 2016: Psychopath Ballads
- 2017: Katla
- 2018: Nectar