Return of Ultraman (帰ってきたウルトラマン - Kaettekita Urutoraman - roughly meaning "Ultraman Has Returned") is a tokusatsu SF/kaiju/superhero TV series, and is the 4th Ultra Series.
Eiji Tsuburaya originally intended for the Ultra Series to end with the 1967 series Ultra Seven, but Ultraman was too famous a character to keep down. After Eiji's passing in 1970, his son Hajime Tsuburaya (who took over Tsuburaya Productions until his death in 1973) revived the Ultra Series with Return of Ultraman.
Featured in this show is a new Ultraman named "New Ultraman" (新ウルトラマン - Shin Urutoraman), or just "Kaettekita Ultraman" (帰ってきたウルトラマン), like the show's title. In the late 70s-early 80s, however, he was renamed "Ultraman Jack" (ウルトラマンジャック - Urutoraman Jakku) for licensing, after Tsuburaya and Bandai (which had just bought the Ultraman toy license in Japan) held a contest for children to pick a new name for this Ultraman. Although he is called "Ultraman Jack" for licensing in and out of Japan, he is still sometimes referred to as "New Ultraman"/"Kaettekita Ultraman", especially by some fans (and also in some official sources).
Also of note is that this is quite possibly one of the few Ultraman/Ultras that requires no tool (like the Beta Capsule) to transform with. Hideki Gô, the human host for New Ultraman, just raises his hands to transform at will when New Ultraman signals him to do so (or sometimes against his will in a very desperate situation!).
For the first time, the late Ishiro Honda, best known for his work on the Godzilla movies and other classic Toho tokusatsu, works on the Ultra Series, and has directed some of the episodes of this series, including the first episode (titled "All Monsters Attack" - 怪獣総進撃 - Kaijû Sôshingeki, which is the same as the Japanese title for the film Destroy All Monsters!). (Wikipedia)