Among the instruments up for grabs will be Gilmour’s 1969 Black Stratocaster which he played on albums including The Dark Side Of The Moon, Wish You Were Here, Animals and The Wall.
The charity consists of lawyers and environmental experts who are fighting against climate change with the aim of protecting nature and the environment.
Gilmour tells the charity’s website: “The global climate crisis is the greatest challenge that humanity will ever face, and we are within a few years of the effects of global warming being irreversible.
“I hope that the sale of these guitars will help ClientEarth in their cause to use the law to bring about real change.
“We need a civilised world that goes on for all our grandchildren and beyond in which these guitars can be played and songs can be sung.”
ClientEarth’s CEO James Thornton adds: “I’d like to express my deep and heartfelt gratitude to David Gilmour for this utterly remarkable gift.
“David has a long history of supporting charities and I am honoured that he has chosen ClientEarth to benefit from this landmark auction.
“ClientEarth is working across the world, using the law to fight climate change and protect nature, and this gift will do an enormous amount to support our efforts to ensure a sustainable and hospitable planet for future generations.”
With the sale due to take place in the coming hours, the Christie’s website have posted an interactive 3D look at the instruments up for auction.
Viewers can click on each guitar and learn more about their history and the estimated price they are expected to sell for.
Last month, Gilmour launched a trio of podcasts to give further information about some of the guitars up for sale.