Mr De Lacy, who was born in Cairns, was an underground coal miner and farmer before entering the world of politics.
He was an MP for 15 years, and served as treasurer under the Goss Labor government from 1989-1996.
"Keith was part of Wayne Goss's government, which will long be remembered for its reforms," Queensland Premier Annastacia Palaszczuk said.
After his political stint, Mr De Lacy became involved in a range of companies, serving as president of the Australian Institute of Company Directors where he received the boards esteemed Gold Medal.
He was also awarded a Member of the Order of Australia for his services to Queensland.
The Premier today expressed her condolences to Mr De Lacy's daughters, Jonnie, Jacquie, Toni and their families.