Ultraseven (ウルトラセブン, Urutora Sebun) is a Japanese tokusatsu science fiction television series created by Eiji Tsuburaya. It is the third installment in the Ultra Series and was produced by Tsuburaya Productions. The series aired on Tokyo Broadcasting System from October 1, 1967 to September 8, 1968.
The original line of Masudaya talking vinyls contained at least 4 different Ultraman characters, but when the line was resurrected in the late 1990s, only one, Ultra Seven, saw production. Evidently, Ultra Seven is considered the most popular of the Ultramen (at least, according to Wikipedia), so I suppose it would make sense in that context.