US President Donald Trump has formally designated Antifa as a “major terrorist organisation,” days after the assassination of conservative activist and his close aide, Charlie Kirk.

In a post on Truth Social, Trump described Antifa as a “sick, dangerous, radical left disaster” and said he would recommend investigations into individuals and entities funding the group. However, he did not specify the legal framework his administration would use to classify Antifa or the concrete measures to be taken against it.

Antifa, short for “anti-fascist,” is widely seen as a loosely affiliated movement with no central leadership or formal structure. Its supporters have been active in counter-protests against far-right groups, but critics argue it has engaged in violent tactics.

Trump has repeatedly blamed left-wing radicals for rising political violence in the United States. In the aftermath of Kirk’s death, he contrasted “radicals on the right,” who he said act to prevent crime, with “radicals on the left,” calling them “vicious” and “politically savvy.”

On September 10, Kirk, 31, was shot during a campus event at Utah Valley University and later died of his injuries. Prosecutors have charged Tyler Robinson with aggravated murder and six other counts, announcing they will seek the death penalty.

Court documents suggest Robinson’s mother told investigators that her son had recently shifted toward left-leaning politics, becoming more supportive of LGBTQ+ rights and entering a relationship with a transgender woman.

Kirk founded Turning Point USA (TPUSA) in 2012 at age 18, growing it into a major conservative student organization with over 800 chapters nationwide. TPUSA played a key role in mobilizing young conservative voters in the 2024 election and boosting Trump’s re-election bid.