Casio Computer Co., Ltd. is a Japanese multinational consumer electronics and commercial electronics manufacturing company headquartered in Shibuya, Tokyo, Japan. Its products include calculators, mobile phones, digital cameras, electronic musical instruments, and analogue and digital watches. It was founded in 1946, and in 1957 introduced the world's first entirely electric compact calculator. It was an early digital camera innovator, and during the 1980s and 1990s, the company developed numerous affordable home electronic keyboards for musicians along with introducing the world's first mass-produced digital watches.

Casio's products include watches, calculators, electronic keyboards and other digital products such as digital cameras (Exilim series), film cameras, cash registers, laptops and sub-notebook computers, mobile phones, PDAs (E-Data Bank), electronic dictionaries, digital diaries (early PDAs), electronic games, computer printers, clocks, and portable televisions.

In the 1970s and 80s, Casio was best known for its electronic (including scientific) calculators, electronic musical instruments and affordable digital watches incorporating innovative technology. Today, Casio is most commonly known for making durable and reliable electronic products. The G-Shock range of shock-resistant watches is also very popular, with the original 1983 G-Shock DW-5000C being highly sought-after by collectors. The scientific calculators made by Casio especially the CLASSWIZ series of calculators are known for being affordable while incorporating a host of functions as compared to their competitors.

Casio also makes products for local markets, including "Prayer Compass" watch series designed to help Muslims pray on time and in the right direction.