Marcos is of Spanish and Italian origin, meaning "warlike" or "dedicated to Mars". It was originally a Roman family name that became popular as a given name during the Middle Ages in Spain. The name Marcos is associated with Saint Mark, one of the four Evangelists and the author of the second Gospel in the New Testament. This has contributed to its popularity among Christians throughout history. In some languages, such as Portuguese and Italian, Marcos is used interchangeably with the name Mark. Notable individuals named Marcos include Brazilian footballer Marcos Everson de Paulo and Spanish actor and director Alejandro G. Iñárritu, born Carlos Alberto Iñárritu Santos-Cacho but professionally known as Alejandro González Iñárritu.
The name Marcos experienced a significant increase in popularity over time, with a total of 52,345 births recorded between 1888 and 2023. The number of annual births fluctuated greatly, ranging from just 5 in 1888 to a peak of 1,350 in 1996. The most notable periods of growth were from the late 1940s onwards, with consistent increases until the late 1990s. However, there has been a decline since then, with fewer than 700 births recorded annually in recent years.