Ryoko is a key fictional character in the anime series Tenchi Muyo!, produced by AIC. Although the details of her character differ among the various series, Ryoko is typically portrayed as an attractive, semi-reformed space pirate who is madly in love with the main character of the series, Tenchi Masaki. In the various series, Ryoko is depicted as impulsive, hedonistic (with a propensity for good), poor, often immodest, recklessly violent, and hot-tempered, although she sometimes reveals her more emotional and vulnerable side.

In the anime, Ryoko maintains an intense rivalry with the character Ayeka, who also vies for Tenchi's affections. The conflict between the two often arises from their decidedly different personalities, with Ryoko being the troublemaking tomboy and Ayeka being the well-mannered but often snooty aristocrat. The level of rivalry can vary from being equitable to a pair of siblings squabbling or an all-out brawl.

While the name Ryoko is a common female given name in Japan, in this case, it is written with very unusual kanji. Ryoko's name can be translated as demon carrier and is stated to mean The Devil Caller in the OVA series.