The following is a list of the major characters from the anime and manga series Tenchi Muyo! Ryo-Ohki and its spin-offs Tenchi Muyo! GXP, Tenchi Muyo! War on Geminar, Tenchi Universe, Tenchi in Tokyo, and Ai Tenchi Muyo!.

Masaki Kajishima and Hiroki Hayashi, who both worked on the Bubblegum Crisis OVAs, cite the show as being the inspiration for Tenchi Muyo! Ryo-Ohki.

In an interview with AIC, Hayashi described Bubblegum Crisis as "[a] pretty gloomy anime. Serious fighting, complicated human relationships, and dark Mega Tokyo." Hayashi and Kajishima thought it would be fun to create some comedic episodes with ideas like the girls going to the hot springs, but these ideas were rejected by their sponsors. Hayashi explained that having a cast of several characters of one gender and a single one of the other gender was a trend at the time; he wondered what it would be like if Mackey (Sylia's brother) was a main character of a show, reversing the scenario in Bubblegum. This became the basis for the Bubblegum Crisis.

In designing Ryoko, Kajishima and Hayashi were inspired by the American sitcom I Dream of Jeannie and wanted to use her in their works. In the first episode, Tenchi opens the sealed cave, a reference to the Jeannie's bottle, and a "cute witch" jumps out. Hayashi said that Tenchi is "sort of" based on Mackey, and that after Tenchi and Ryoko, the rest of the girls were designed as original characters to balance the picture in the very early concepts of the series.

Tenchi Masaki (柾木 天地, Masaki Tenchi) is the title character of the Tenchi Muyo! series. Tenchi's name means "Heaven and Earth." It is the same as "Tenchi" in the Shinto creation myth detailed within the Kojiki, which contains some of Japan's oldest myths and legends.

In the OVA-based continuities, Tenchi is the first prince of Jurai, grandson of a Juraian prince named Yosho, and of an Airaian priestess named Airi. He obtains of a "'Master Key" called "Tenchi", also known as the Tenchi Sword (Tenchi-ken), that can form a lightsaber-like blade and later receives a special ring from Tsunami that can create a Juraian battle suit for him and acts as a "Guardian System" which protects him. Tenchi also has the innate ability to create kou-ou-yoku ("Light Hawk Wings") (believed to be the only non-ship entity able to do so until encountering Z in OVA 3), and the ill-defined ability of Material-Energy Conversion. Tenchi initially lives in the city with his father to attend school and visits his grandfather's shrine every summer, where he trains to become a Shinto priest and learn his family's special style of swordsmanship (which happens to be particular to members of Jurai's Royal Family). The house is permanently relocated next to the shrine after a battle between Ryoko and Ayeka, and Tenchi lives in the house with the girls while refusing to get intimate with them. Tenchi no longer attends school, after the school was decimated during the encounter with Ryoko in OVA 1 (but rebuilt as of OVA 3).

Tenchi suffers a great deal of stress as he tries his hardest to be a gentleman while most of the women within the household will take every opportunity to display their attraction for him. In the third OVA series Tenchi is discovered to be engaged to Noike (step-aunt of Ayeka and Sasami). The arrangement was done by Tenchi's great-great-grandmother, known better as the "Devil Princess of Jurai", Seto Kamiki Jurai. Tenchi also found out around this time that he has an 80-year-old sister named Tennyo Masaki, who looks like his late mother, Kiyone. Tenchi learned from his grandfather, Katsuhito, that since Earth is a developing civilization, the Masaki clan must keep their true presence hidden since they do not age at the same rate as Earthlings, and those who are born into the Masaki family are also kept from these secrets until they reach adulthood. After a climactic battle between the three Goddesses, the truth behind everything that has happened was linked to the three. They decided to change the timeline in order to repair the damage that they have done, and Tenchi, in his altered timeline, doesn't get to meet Noike. However, Noike, along with Fuku, traveled into the past and altered the message Mihoshi was to send to her family (the message was originally altered by Z) so that she would meet Tenchi.

Tenchi is one of the most powerful characters in the series, but is too young and immature to have full control over his Light Hawk Wings and other abilities. He is a competent swordsman and martial artist capable of superhuman feats thanks to his Juraian blood, but has only displayed his abilities during dire situations, such as during his duel with Kagato, his escape from a black hole, and his final confrontation with Z. The full extent of Tenchi's powers is limitless, as he was stated outright by the Choushin to be as powerful as them, the same beings who created all of existence and transcend space and time. When he started to manifest his higher self, it almost instantly destroyed all of existence, forcing the Goddesses and his own future self to intervene and prevent a catastrophe (in the new "altered" timeline, when Noike secretly fired the Choubimaru's cannon to collide with the Earth, Tenchi projects his Light Hawk Wings to stop it, a total of six wings, rather than the usual 3 wings he had before prior to the event.)