Cher is gonna be pissed! The beloved L.A. Zoo elephants she went to bat for — Billy and Tina — were secreted outta the zoo under cover of darkness last night … TMZ has learned.

Sources connected to the L.A. Zoo tell us Billy and Tina were removed around 1:30 AM Tuesday and, presumably, loaded up to be shipped to Tulsa Zoo — a controversial move that prompted protests and an angry letter to L.A. Mayor Karen Bass … which Cher and several other celebs signed.

We’re told the elephant exhibit at L.A. Zoo was empty Tuesday morning — no elephants, no keepers and the electric perimeter fence was off … clear indications the animals were on their way to Oklahoma.

Our sources say the elephants were put into crates and loaded onto a semi-truck for the transfer to Tulsa Zoo. It’s unclear whether how long the trip will take.

We reached out to several L.A. Zoo officials, but no one’s called back, and L.A.’s Deputy Mayor — who oversees the zoo — hung up on us.

Advocates for Billy and Tina have been all over the L.A. Zoo for years, because Billy and Tina, Asian elephants, have been kept in an enclosure far too small for them.