The one accessory that’s a must on Kentucky Derby Day is a hat.

And swimsuit model and actress Kate Upton led the way in the fashion stakes at Churchill Downs in a large white boater with black band.

She poured her stunning curves into a classy dark green knee-length dress with a v-neck.

The 23-year-old Sports Illustrated cover girl left her signature blonde locks loose under the hat, framing her face in relaxed long curls.

She kept her make-up light, accentuating her eyes with mascara and liner and opting for light pink lip gloss and a touch of blush.