The service for Ian Campbell – also known as John Harley – will take place at Portchester Crematorium in Hampshire on Tuesday 24 August at 13:00.
Mr Campbell passed away alone in the Queen Alexandra Hospital in Portsmouth, aged 78.
Having served in Burma, Saudi Arabia, Ireland and Malaysia, it is thought the deceased commando's only family members live in Canada – prompting the Royal Marines Charity (RMA) to pay for his funeral.
Forgotten Veterans (FVUK), another organisation which is spreading word about the funeral, wrote on Facebook: "Sadly Ian (John Harley) Campbell died alone in the QA Hospital recently and us at FVUK, Portsmouth Council and the Royal Marines Charity have worked tirelessly to pull together to find friends and family.
"The RMA have paid for his funeral and we have done our very best to give this long-serving veteran the funeral he deserves."
The post went on: "We now need the community, civilians, bikers and Standard Bearers from across the board to make sure he certainly isn't buried alone."