The Casio F-91W, launched in 1989, is a quartz digital watch with a resin case of about 35 mm, a resin strap, an LCD display with a backlight, a daily alarm, an hourly chime and a stopwatch. It is splash resistant rather than a diver, and Casio quotes a battery life of around seven years. I give the size as approximate, as sources differ by a millimetre or two.

The F-91W is one of the best-selling watches ever made, with sales commonly cited in the millions per year, and its price has stayed very low for decades. Its design has barely changed since 1989, and it is a fixture of street, military and fashion use.

The community regards it as a design classic and a gateway watch, loved for its simplicity and accuracy for the price, and often modified. It remains in production.