Owner Stewart Donald will end his six year association with the National League club when he finds a buyer.
Under his ownership, the club won the National League South and enjoyed good FA Cup runs, but progress in the top flight wasn't what he would have wanted.
Stewart invested millions in not only the team but the stadium, with all four sides of the Silverlake transformed thanks to his backing.
He leaves the club totally debt free and is keen to hear from any parties wanting to take them forward.
Eastleigh won 4-1 at Solihull Moors on Saturday to end to end the season in 14th place.
In a statement, the businessman confirmed the decision has been an "emotional" one.
It read: "It is with great sadness and regret that I have to inform the Eastleigh fans that I have put our football club up for sale. I have spent over six years at the club and from the very first moment I arrived I have been welcomed and treated with great respect and kindness and I am truly grateful for the support everyone has given regardless of how well the team have performed at any given time.
"It is an emotional decision for me and one that I did not expect to have to make. However, with my potential involvement in Sunderland, it is a condition that I must relinquish control of Eastleigh. If the rules were different I would have loved to remain with the club for many years to come.
"Eastleigh has become, and will always be, extremely close to my heart. I have always tried to look after the club to the best of my ability and this will never be more important than now when considering perspective new owner/s.
"The football club is in the strongest financial position it has ever been in. With a much-improved stadium and increased revenues enabling the club the ability to seriously compete in the top tier of non-league football and whilst I have been unable to deliver League football, I hope the fans will reflect on my chairmanship as a positive one.
"My focus now must move to finding a suitable owner who will understand the ethos of the club. It is vital to ensure that the club continues to provide affordable football and progresses on the field whilst incurring absolutely no debt. I always ensured Eastleigh was run without debt and that any money provided was never going to create any debt.
"I would like to assure the fans that I will not charge for the sale of the club and do my very best to ensure that the club is passed to an individual or group that understands these principles and is committed to continuing them.
"I will obviously remain as owner for a short period and hopefully, I will get to see some of you before I depart and if not I will return and watch as many games as I can.
"Thank you all again for making my ownership such an enjoyable experience."