Cher doesn't seem to trust her son Elijah to make sound financial decisions right now ... so the singer-songwriter has filed for a conservatorship to control access to his money.

In documents filed Wednesday, Cher claims her 47-year-old son is "substantially unable to manage his own financial resources due to severe mental health and substance abuse issues."

The documents state Elijah is entitled to regular payouts from a trust set up by his late father, legendary musician Gregg Allman, but Cher is concerned the money will immediately go toward drugs rather than basic living necessities.

The 77-year-old singer argues that she, as Elijah's mother, is in the best position to serve as conservator and also notes two of Elijah's siblings have nominated her to fill the role.

She also takes a dig at Elijah's estranged wife, Marieangela King, who she says is undermining Elijah's attempts at getting the mental health and substance abuse help he needs.

As we previously reported ... Marieangela accused Cher of kidnapping Elijah to force him into rehab last year, a claim Cher has unequivocally denied.