Ryan Lochte -- Parents Swimming in Debt, Facing Foreclosure

US Olympic swimming champion Ryan Lochte might have to parlay his newfound fame into a quick payday to help out the folks ... because TMZ has learned, his parents are allegedly buried in debt ... and could lose their home.

According to a lawsuit filed in Volusia County, FL ... CitiMortgage claims Steven and Ileane Lochte took out a mortgage loan for $258,000 back in 2007 and they were to pay $1,609.58/month.

But according to the bank, the Lochtes stopped making payments in February 2011 -- and now owe $242,239 (plus interest) on the home. The bank is suing to foreclose on the house in order to get its money back.

But there's a lot on the line -- according to the lawsuit, if the sale of the Lochtes' home doesn't satisfy the couple's entire debt ... the bank wants the Lochtes to pay the difference.

Mrs. Lochte filed a motion to dismiss the case last month, but a judge has yet to rule.

Attempts to reach the Lochtes were unsuccessful.