Madison Beer Stuns Assistant with Mercedes-Benz Birthday Gift

Madison Beer splurged for her personal assistant's 30th birthday gift ... and we ain't talking expensive booze or jewelry, more like luxury wheels.

The surprise reveal went down Monday night in L.A. after the singer and some friends celebrated her assistant's birthday. When dinner ended, Madison handed her assistant a bag, but it turned out to be empty. It was also a ruse.

Check out the vid ... you can see Madison pull out a key fob to a brand new Mercedes-Benz C300. Suffice it to say ... Madison's assistant was stunned and damn near speechless.

Helluva gesture, especially 'cause Madison knew about her assistant's car trouble for a while. We're told her assistant's 12-year-old whip kept breaking down. It's a car she used a lot to run Madison's errands and whatnot. Madison also knew her assistant's dream was to one day own a white Benz. Madison delivered, and then some ... a white-on-white model that tends to run upwards of $50k.

Goes without saying, Madison is super close with her assistant, and knew this would blow her mind. She was dead-on, as you can see in the video -- which also reveals a sweet new nickname for boss Beer.