Sega Mark III's reported Japanese launch turns 41

On Oct. 20, 2026, OnThisDayGaming marked the 41st anniversary of a 1985 Japanese release, calling the console the “Sega Mark III/Sega Master System.” ThisDayGaming makes a distinction between the names: It describes the Master System as a later redesign of the Sega Mark III.

segaretrobr dates the Mark III's Japanese launch to Oct. 20, 1985, and says it was remodeled as the Master System for Western markets in 1986. In that account, the anniversary marks the Mark III's Japanese debut, not a same-day Japanese launch for both versions.