Released on August 19, 2010 in Japan.
Choujigen Geimu Neptune was the first game within the series, with the name originally derived from the scrapped Sega Neptune which combined the Sega Mega Drive and 32X into one unit, originally scheduled for release in 1994 or 1995 before the project was dropped after the release of the Sega Saturn.
A television anime series adaptation, titled Hyperdimension Neptunia: The Animation, aired in Japan between July and September 2013.
"Choujigen Geimu Neptune [Model BLJM-60377]"
[AS] "Choujigen Geimu Neptune [Model BCAS-20129]"
[AS] "Choujigen Geimu Neptune [Model BCAS-20165]" (English ver.)
"Hyperdimension Neptunia [Model BLES-01178]"
"Hyperdimension Neptunia [Model BLUS-30701]"