The Spice Girls reunion tour doesn't start until December, but there's a part of Geri Halliwell that's already rockin' -- her abs!

Ginger showed off her taut tummy in a white bikini, while jet skiing in St. Tropez on Saturday. Spice up your life!

Today is Geri's birthday. She turns an alleged 35-years-old. Zigazig HA!