The 'Taken' actor received the prestigious accolade – the highest the Ballymena Borough Council can award one of its citizens - at a ceremony in the Northern Irish town.
Liam, 60, spoke of his pride in his Northern Irish roots saying: "Enormous strides have been made in my native Northern Ireland in the past decade, demonstrated by political, social and economic changes that came about through a combination of courage, generosity and persistence."
Speaking ahead of the ceremony, Mayor P J McAvoy told the BBC: "This is a significant civic occasion but we have been at pains to keep the formalities to a minimum, in keeping with Liam's relaxed style.
"It will also be a real Ballymena-style celebration, with some of our fantastic local talent providing the music; Ballymena students providing their own cinematic tribute to Liam's life and work and local produce providing guests with a literal 'taste of the region'.
"Liam will find himself very much at home when he steps onto the stage to speak to his Ballymena audience, for he started his acting career by treading those very boards as a young member of the Slemish Players."
Only three people have previously been awarded the freedom of Ballymena: Ian Paisley, former rugby player Syd Millar and former mayor Sandy Spence.