While Alex Rodriguez keeps striking out, Derek Jeter strikes gold ... because he just unloaded his NYC condo for a cool $15.5 mil.

Jeter just sold his penthouse in the Trump World Tower to Brazilian magnate Silvio Luiz Reichert, says the NY Daily News. The four-bedroom apartment has 16-foot floor-to-ceiling windows, a living room, billiards room, piano lounge, wet bar, hardwood floors and an actual word-burning fireplace.

D.J. originally asked for $20 mil, but dropped the price and sealed the deal last month. Fear not ... there are no cardboard boxes in Derek's future, because he still owns a giant mansion in Tampa.

As for A-Rod, he's still trying to dump his $38 million Miami mansion. So far, no takers. Maybe he should call Raul Ibanez.