The 'Ain't Nothing Changed' rapper - who won the NME Award for Best British Solo Artist this year - joins previously confirmed acts Wolf Alice, Australian group DMA's and Sheffield quartet The Sherlocks at the special one-day festival at the London landmark on June 29.
Liam will be in good company as fellow Mancunians Twisted Wheel, and Trampolene - both of whom he's toured with in the past, the latter as a solo act and the former with Britpop legends Oasis - are also performing along with Dream Wife, Belako, Easy Life and Hey Charlie.
The 'Wall of Glass' hitmaker previously hinted one of the acts would be his ''biblical brother'', the signature description, which he reserves for people he thinks are god-like.
Replying to a fan on Twitter who previously tried to tease the acts out of the rocker, Liam replied: ''Mate I can't tell ya but I have a biblical brother joining me now run of and spread the butter you nutter (sic)''
Many fans believe he was referring to former Verve frontman Richard Ashcroft, who supported Liam on his North American tour.
The last time Liam performed at Finsbury Park was with Oasis back in 2002, and he's hoping it will be just as ''dangerous''.
He said previously: ''I loved that gig, man. It was really f**king dangerous and I liked it. So hopefully we'll have a bit of the same.''
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