Federal prosecutors say a Grand Jury in Miami indicted the "Beautiful Girls" singer and his mom, Janice Turner, hitting each with one count of conspiracy to commit wire fraud, and 5 counts of wire fraud.

The charges, announced Friday, are for allegations Sean and his mom cooked up a scheme to swindle multiple businesses out of jewelry, luxury vehicles and other goods.

Federal prosecutors say Sean and his mother unjustly enriched themselves by falsely claiming they sent money transfers to pay for high-end goods ... and then kept the stuff even after it was discovered the payments never went through.

The feds claim Sean and Janice obtained more than $1 million in property through their alleged scheme -- including ripping off a car dealer for a $160K Cadillac Escalade and jewelers for $480K worth of bling ... all without paying a dime.

Sean and Janice, who were arrested in May following a raid on his Florida mansion, appeared in federal court Friday for the first time.

They are looking at some seriously HARD time if convicted ... we're talking a max of 20 years in prison on each count, for each of them. Remember, mother and son are facing 6 counts.