Ranger Alan Owens was awarded the prestigious honour for work in Afghanistan, developing “a level of empathy with the local population which no amount of fighting could establish”.
Mr Owens, from Portadown, Co Armagh, was presented with the Military Cross in March 2009.
But it, along with other military memorabilia is listed for sale on eBay under the title “real British military cross medal”.
The listing includes a starting bid of £25,000, with the option to “Buy It Now” for £100,000. Last night, no bids had been made.
The citation, also included on the listing, reads: “Owens' role was to mentor the (ANA) Afghan National Army, but his actions showed leadership and maturity well above that expected of his rank and experience.
“His presence fortified the ANA and galvanised their resolve, especially as light began to fade.
“Owens displayed courageous individual actions in the face of the enemy. He also demonstrated a clear grasp of the key principle of counterinsurgency.
“By checking for civilian casualties he engendered a level of empathy with the local population, which no amount of fighting could establish. His performance in Kajaki bore the hallmarks of personal bravery and selfless commitment. His acts, thoughts and valour are most deserving of high official recognition.”
Also for sale are a Northern Ireland medal 2003, Iraq Medal 2005, Afghanistan Medal 2006 and 11 Letters Of Congratulations From top officers.
An MoD spokesman said Mr Owens had now left the Army. He said: “The military cross has been awarded to him and he is free to do with it as he wishes.”
Mr Owens said he did not want to discuss the sale of the medal.