Fonda discusses her time in Northern Ireland and her arrest last year while protesting to highlight the climate crisis.
Garda whistleblower Majella Moynihan, who revealed her treatment at the hands of her superiors in the Gardaí will also appear on tonight's show, telling Tubridy how her's is a story of hope.
US President Donald Trump's niece, Mary will discuss her book controversial book and why she think's President Trump is out of his depth in the White House, before presenters Ant and Dec chat about tracing their Irish roots and the return of I'm a Celebrity.
Dublin GAA star Bernard Brogan will be in studio, while The Academic will perform their new song Acting My Age.
The Late Late Show will be on RTÉ One at 9.35pm.