Kylie and Kendall Jenner's Vacation Villa's a Mexican Paradise

Kylie and Kendall Jenner are living like queens south of the border ... soaking up the sun in a castle by the sea.

The billionaire and her model sister are treating themselves to a Mexican getaway, shacking up in the super luxurious Ocean Castle Sol de Oriente in Costa Careyes ... and ya gotta see their digs.

The 6-bedroom villa sits atop the Peninsula de las Estrellas -- that's Spanish for stars -- and it's surrounded by a 360-degree infinity pool offering panoramic views of the ocean and beach.

The private estate goes for $6,500 a night and has room for 12 ... but this girls' trip is reserved for Kylie, Kendall and Stassie Karanikolaou.

The fortress is very camera-friendly too ... Kylie, Kendall and Stassie all have been posting tons of pics out by the pool, from sunrise to sunset.