What is Eleven's birth first name?

Eleven’s birth first name is Jane. She was born Jane Ives before becoming known as Eleven and later taking the legal name Jane Hopper.

Her biological mother is Terry Ives, who was involved in experiments connected to the CIA’s MKUltra program while pregnant. Dr. Martin Brenner took the child from Terry and brought her to Hawkins National Laboratory, where she was identified primarily by the test-subject number 011. That number became the name by which she was most often known during her childhood.

The name Jane is easy to confuse with the names of other important characters. Sarah was Jim Hopper’s deceased biological daughter, Holly is Mike Wheeler’s younger sister, and Kali Prasad was another child subjected to Brenner’s experiments. Kali is sometimes described as Eleven’s sister, but she is not Eleven’s birth name or biological sibling.

After Hopper received a forged birth certificate in season 2, Eleven became legally Jane Hopper and was able to attend the Snow Ball at Hawkins Middle School. In everyday conversation, however, Mike and her friends commonly call her El, while “Eleven” remains her best-known identity.