The Original Red Knight is from Arthurian Legend like the Black Knight and Green Knight. The Red Knight prominently appears in the tales of Percival as his early enemy. In other tales he is brother to the Green Knight and the Blue Knight. Gawain and Galahad used the name in other legends.
In comics there have been many different interpretations of this character with the earliest in comic being a series in Cyclone Comics in 1942.