Comedian and actor Robin Williams is to donate the profits from his show in Christchurch to rebuilding the earthquake-hit city.

Half of the profits will go to the Red Cross and the other half to the mayoral building fund.

The funnyman is doing two shows in New Zealand on his 'Weapons of Self Destruction' tour in November - only the Auckland show will "pay the bills".

Williams hopes the donation will help with the extensive rebuilding work that needs to be done.

"It is devastating what has happened in Christchurch but from what I have learnt, the people there are incredibly resilient.

"The first quake of 7.1 would have been traumatic enough but I understand that since then, the people of Christchurch have experienced close to 3000 aftershocks. That is an unimaginable trauma to have to endure."

Red Cross spokesman Paul Scoringe was thankful for Williams' donation.

"It's a very kind gesture from Robin Williams for which we are very grateful. We'll be thanking him on behalf of the Red Cross and Cantabrians."

Williams' charitable behaviour comes after a quip he made to the Herald in August that he was in it for the money to pay his bills.

"I have been doing small movies. Small movies are great to do but they don't pay the bills. Literally ... I'm playing auditoriums. We are both making money the old-fashioned way."

A few tickets are still available for the Christchurch and Auckland shows on Friday and Saturday.