|This article is about a/an monster in Kaizoku Sentai Gokaiger.|
Great Scientist Zaien (大科学者ザイエン Daikagakusha Zaien) is one of Space Empire Zangyack's top scientists.
A scientist in the employment of the Zangyack, he was a specialist at modifications, using his abilities to turn beings into cybernetic beings with no memories or concept of their former life or identity.
Zaien was the one who originally performed the operation that turned Sid Bamick, Joe Gibken's friend, into the deadly Zangyack cyborg Barizorg. His plan to assist the Zangyack with their conquest was to capture the greatest athletes of Earth and modify them into similar cyborgs, creating an army that would crush the Earth forces.
Though capturing several athletes, his attempt to capture a boxer was stopped by Joe and Ahim de Famille; while the siege upon his Earth headquarters was stopped by the entire Gokaiger team, first with the greater power of the Liveman, then by Joe taking him out with Sid's specialty move. After grown by his rival scientist Insarn, he is brought down by Hurricane Gokai-Oh.
- Height - 195cm (Giant form - 48.8m)
- Weight - 139kg (Giant form - 347.5t)
- The voice actor for Zaien is Joji Nakata, who played the main Liveman villain Great Professor Bias. This is particularly notable given his episode is a Liveman tribute.
- His name is a pun on "science"
- His motifs are the ones of a brain and of a jellyfish. His appearance is also based on Great Professor Bias.
- This Action Commander greatly resemble Jinzo from the Yu-Gi-Oh! card game.