Just ask Gilbert Arenas' fiancée ... who returned the favor, asking the former NBA star to marry her just weeks after he got down on one knee asking her the same question.

Confusing, we know. Here's a breakdown.

Arenas -- who played 11 seasons in the NBA -- asked his longtime girlfriend Melli Monaco to marry him last month at the Eiffel Tower ... with a massive diamond ring, which the musician/YouTuber revealed on Instagram.

Monaco decided she was in the mood to reciprocate ... and while the couple was hangin' out at a nightclub with friends on Monday, a bunch of bottle girls walked up with a sign that read "Men Wear Engagement Rings Too"

Arenas, as you can see, was highly confused ... that is until he saw Monaco holdin' an engagement ring. Gil gladly accepted ... going crazy after she put it on his finger.

"[Monaco] surprised me with an engagement ring 🤯😏😏," Arenas said in the IG post. "Got me feeling like a #Baddie 🤷🏾‍♂️ City Boys they're giving us engagement rings now 💯😂."

Monaco and the 3x NBA All-Star began dating last year after Arenas shot his shot during her live stream.