The Toyota Prius c (c stands for "city"), also known as the Toyota Aqua (Japanese: トヨタ・アクア, Hepburn: Toyota Akua); "aqua" is Latin for water) in Japan, is a full hybrid gasoline-electric subcompact/supermini hatchback manufactured and marketed by Toyota. The Prius c is the third member of the Prius family, and combines the features of a Yaris-sized car with a hybrid powertrain. The Prius c is priced lower than the conventional Prius and has a higher fuel economy in city driving under United States Environmental Protection Agency test cycles. The Prius c was ranked by the EPA as the 2012 most fuel efficient compact car when plug-in electric vehicles are excluded.

Toyota presented the production version of the Aqua at the 2011 Tokyo Motor Show; presented the U.S. Prius c at the January 2012 North American International Auto Show in Detroit, and launched the Aqua in Japan in December 2011 at a price of ¥1.69 million (US$21,700). Sales in several Asian markets began in January 2012. The Prius c was released in the U.S. and Canada in March 2012. Sales in Australia and New Zealand began in April 2012.

The Aqua is considered the most successful nameplate launch in Japan in the last 20 years. As of January 2017^[update], the Aqua/Prius c is the second most sold hybrid of Toyota after the regular Prius, with 1,380,100 units sold worldwide. Japan as the market leader with 1,154,500 units sold through January 2017. The Aqua was the top selling new car in Japan for three years in a row, from 2013 to 2015.

The Prius C was discontinued in North America at the end of the 2019 model year. It was also discontinued in Australia in early 2020.

The Toyota Prius c concept car was unveiled at the January 2011 North American International Auto Show in Detroit. The design takes cues from the Toyota FT-CH concept vehicle that was shown at the same event in 2010. Toyota explained that the 'c' in 'Prius c' stands for "city"-centric vehicle as it is smaller than the standard Prius and aimed at younger buyers without families who require less cargo space in the rear and fewer of the luxury touches (although passenger space remains essentially the same as a standard Prius). This results in a higher EPA MPG-City Rating than the standard Prius and easier parking in tight spaces.

Together with the introduction of the production version of the Toyota Aqua at the 2011 Tokyo Motor Show, the carmaker also exhibited two other Aqua concepts, the Aqua Kiriri version and the Aqua Piriri.

Built on an enhanced and streamlined Yaris-inspired platform, the Prius c features Toyota's Generation 3 Hybrid Synergy Drive with a 1.5-liter DOHC four-cylinder, 16–valve with VVT-i gasoline engine, the same engine model and displacement as on the earliest Priuses, but is now "beltless". The air conditioner is a self-contained unit containing a motor & compressor powered by the 144-volt traction battery, and the 12-volt battery is charged via a DC-DC converter also powered by the traction battery.

Unlike earlier Prius HSDs, the Prius c incorporates separate planetary gear reduction paths for the ICE/MG (internal combustion engine/motor-generator) one, now better matched to their respective mission functions, in a significantly smaller, lighter weight package. The chain drive found in the Gen 1 and Gen 2 HSDs is also eliminated, replaced by helical gears in the Gen 3 HSD. The MG2 ratio is 2.5:1 rather than 1:1 as on earlier HSDs, thereby allowing the physical size of the MG2 to be reduced to the cross-section of the MG1. The Prius v and Prius Plug-in share this basic Gen 3 design (P410 transaxle, for both of these), but not its specific implementation, and which is unique to the Prius c and its lower maximum weight, and lower HSD net horsepower (P510 transaxle, for Prius c, North America; Prius Aqua, Japan; and Yaris Hybrid, Europe).^{[citation needed]}