Claudia Marcella Major[a] (PIR2 C 1102; born some time before 40 BC) was the senior niece of Roman emperor Augustus, being the eldest daughter of his sister Octavia the Younger and her first husband Gaius Claudius Marcellus.

Some people such as John Pollini also believe that they had at least one son together, whom he identifies as a young boy next to Agrippa on the Ara Pacis.

[5] Octavia Minor married Marcella to the future consul Iullus Antonius, the second son of Mark Antony from his third wife Fulvia who was held in high regard by Augustus.

In 2 BC, Iullus Antonius was forced to commit suicide after being found guilty of adultery with Julia the Elder.

Prior to 1939, scholars believed that Marcella married another husband after the death of Iullus Antonius, namely the Roman Senator and cousin Sextus Appuleius, the grandson of Octavia Major—the older half-sister of her mother— but it has in modern times been accepted that this was not the case.