Gypsy Rose Blanchard says one of her social media pages was hacked ... and she claims the alleged hacker is demanding money to return her account.

GRB says her TikTok was hacked around 1:30 AM Friday ... compromising the account where she has nearly 10 million followers.

Her TikTok bio was changed to read, "Anyone who violates rights becomes a hack freak. rustywrist"

Gypsy claims she's in contact with the alleged hacker, who she says is asking for $400 to give her the account back.

GRB posted some screenshots of her conversation with the alleged hacker ... where she says she's not going to pay the ransom.

It's funny ... the alleged hacker sends Gypsy a bunch of messages before she finally responds, then when she scoffs at the money demand the hacker responds, "You dont have 400$?"

Gypsy tells the hacker all her money is being budgeted towards her bills and soon-to-be-born child ... letting them know she's not a millionaire, "contrary to popular belief."