Sellstrom takes over the Privett Park hot seat from Tony Stares, who was installed in an advisory capacity when Mark Hook stepped down.
As part of the Borough shake-up, revealed in a statement, former chairman Hook and first-team boss Alex Pike have vacated their roles on the board.
Gosport were relegated from National League South last season after two years of financial turmoil.
They have been served five winding-up orders in the past 12 months.
But it is hoped Sellstrum’s arrival will bring an end to the problems.
‘I’ve come in to restructure the debts and help the club work through its financial difficulties,’ said Sellstrom, a Gosport businessman and resident of 30 years.
‘It is not a case of buying the club because it isn’t in any position to be sold at the moment.
‘We are aware the club is likely to face another winding-up order but we already have everything in place to deal with that.
‘One of the first tasks we face is putting payment plans in place to pay off all our creditors.
‘We will also be looking for further investment and sponsorship to move the club forward.
‘I want Gosport Borough to restore its position in the community because I see it very much as a community club.
‘On Tuesday, I will be holding a fans’ forum at the club and let them fire their bullets at me.
‘Then we will take stock of their issues and deal with them where we can.’ Mark Adams OBE will be appointed as executive officer and join Sellstrom on the board. Click here to read Borough’s statement.