Diogo Alves (born Diego Álvarez; 1810 – 19 February 1841) was a Spanish serial killer and robber.

After changing jobs several times and ceasing to write to his parents, he began to drink and gamble, meeting up with innkeeper Maria "Parreirinha" ("little grapevine") Gertrudes.

He robbed poor passers-by and then dumped them from a height of 60 meters to simultaneously avoid identification and present the deaths as suicides, a ploy which initially succeeded in hiding the crimes.

Scientists could never explain what led him to buy a false key for the Aqueducts, where he was hiding, and how many people he had robbed and killed.

The severed head is currently in the anatomical theatre of the University of Lisbon's Faculty of Medicine, following the formation of a phrenology cabinet made by José Lourenço da Luz Gomes, which allowed the preservation of Alves' skull, along with that of Matos Lobo (one of the last people to be executed in Portugal) in the old medical-surgical school.