The cross-sector partnership, which comprises 12 organisations including Crusaid, the National Aids Trust and the Terrence Higgins Trust, has been formed to add weight to the annual day of action.
The ice sculpture is yet to be commissioned, but will weigh between 10 and 15 tonnes and will lie flat on the square at about knee-height. It will serve as a temporary monument to HIV and Aids and people will be able to add their own red ribbons to show solidarity.
The Greater London Authority has granted permission for both the sculpture and for a message board above it, which will show news about people raising awareness across the UK.
The National Aids Trust has enlisted the services of PR company Edelman to build a website to mobilise support for the day of action from a broader audience. Many websites will display red ribbons that are link buttons to the worldaidsday.org site, which is set to launch this month.
The World Aids Partnership campaign will use this year's World Aids Day to challenge the misconception that HIV is only an issue for specific minority groups. The campaign tagline is: "HIV is an issue for everyone and everyone can do something to make a difference".
It is designed to demonstrate that Aids reaches beyond Africa, and that the disease is on the increase in the UK. One third of the people who have HIV in the UK are unaware that they are carriers.
Deborah Jack, chief executive at the National Aids Trust and a spokeswoman for the partnership, said: "The Trafalgar Square event is a unique opportunity for people to show their support for the 48 million people worldwide living with HIV and will help to chip away at the stigma."