The 'massive' Lego statue is a life-size model of a cyclist and his bike.
It is made entirely of Lego and is complete with display case, the charity said.
In a social media post, St George's Crypt said: "A unique creation with one of the world's favourite toys, this model is the perfect display piece for any office space, reception area, or hallway.
"Each day, thousands of commuters in Leeds stop to take a look and now this unique piece can be yours.
"Lego models of this scale are rare collector's pieces and are not often found for sale."
The listing - available to view here - has a starting price of £1,000.
The auction is set to end on Saturday, July 31.