The former IRA commander turned Deputy First Minister died on Tuesday after a short illness.
Bill Clinton, Tony Blair, an Taoiseach Enda Kenny and President Michael D Higgins will be among those at Requiem mass at St Columba’s Church at 2 this afternoon.
It'll be the second funeral of the day attended by the President who'll go to footballer Ryan McBride's service in Derry this morning.
However it looks like the DUP's Arlene Foster is to make a last minute decision on whether she will go or not.
The former First Minister still hadn't confirmed her attendance by late last night.
In Derry, well-wishers queued outside the McGuiness family home in the Bogside to pay their respects.
And thousands more people are expected to bring the city to a standstill as people say farewell to one of its famous sons.
