A microfilm reader or microreader is a device that uses a lens and source of light to magnify miniaturized text and accompanying images that have been printed on a roll of 16 mm film (100 cm or 215 cm in length) or 35 mm film (100 cm in length), which is also known as microfilm or "roll film."

Throughout the 20th century, many commercial organizations and government agencies used microfilm as the main medium to store large amounts of text from books, periodicals, and records until the advent of modern computers, which offered instant access to content and additional storage and cost-savings advantages over microfilm. The need and production of complementary microfilm readers therefore fell with the need for microfilm, but they are still used today to view stored content on microfilm that has yet to be converted into a digital format.

The development of the microfilm reader began when John Benjamin Dancer produced one of the first recorded microphotographs in 1839. Dancer, an English optical instrument maker, was experimenting with the newly announced Daguerreotype photography process when he placed a microscope lens in a camera, then produced a photograph with a 160:1 reduction ratio. Dancer continued experimenting with microphotography over the next decade, but it was not until 1853 that he captured text onto a microphotograph for the first time: 680 letters inscribed on a monument tablet, which he mounted onto 3 × 1 inch slides that could be read with his 100× microscopes, which became the first predecessor of the microfilm reader.

During this period, many other inventors and practitioners in Europe experimented with capturing and producing photographs of text at reduced dimensions, such as Alfred Rosling's photograph of a page from the Illustrated London News, creating a new novelty industry. The Daguerreotype process, which produced photographs on a copper plate, was the dominant form of photography until the 1850s, when it was replaced by Henry Fox Talbot's "calotype" process that produced a negative image onto paper, which was in turn eventually replaced by George Eastman's nitrocellulose film towards the end of the century.

In the winter of 1870–71, during Prussia's siege of Paris, the French businessman and photographer René Dagron traveled to French-held territories behind enemy lines, where he was contracted to copy documents and personal messages from French officials onto microphotographs, which he dispatched to Paris using carrier pigeons; and if the messages were received, the microphotographs were projected by a "magic lantern", another early form of the microfilm reader. The magic lantern is a type of projector that has been around since at least the 17th century, using candles, then oil as the source of light, and was used primarily for entertainment.

Throughout the first two decades of the twentieth century, roll film went through much development and improvement by making cellulose less flammable. Cameras became more affordable for consumers, such as the $1 Kodak BROWNIE Camera, which contributed to the growth of the motion picture industry. Despite the widespread use of film in the beginning of the century, it still was not used as a form of storage in a commercial setting until 1925, when New York banker George McCarthy invented the Checkograph. Designed as a way for banks to detect fraud and store records permanently, the Checkograph snapped photographs of several checks simultaneously then printed the micro images onto Kodak 16 mm film, which was viewed with a handheld magnifier or a Kodak projector such as the Kodascope, a new form of the microfilm reader.

Books were also being transformed and converted to microfilm during this time, and unique readers were developed for this trend. In 1920, retired Navy Admiral Bradley Allen Fiske filed his first patent for a handheld reading machine that could magnify the microprint of manuscripts and books. Filing eleven patents from 1920-1935, Admiral Fiske's earlier designs resembled a two-eyepiece lorgnette but were later built with a single-eye viewing scope. All of his designs included a roller that shifted the eyepiece along the reading material, which at first were printed on long sheets of paper, then later film. While Admiral Fiske's reading machine, the "Fiskeoscope," never became a commercial success, it did influence the designs of handheld film readers that were produced decades later.

In 1930, the writer and impresario Robert Carlton Brown published an essay titled "The Readies" in the international journal transition, proposing an electric, portable reading machine that used a 4-5 inch magnifying glass to view microfilms of books. However, he adjusted the medium in his 1931 book, "Readies for Bob Brown's Machine," when he stated that books would be printed "on a ribbon of tough impressionable material," implying ticker tape, and that words would move in a single stream across the screen as opposed to viewing paragraphs or pages at one time, the speed of which could be controlled by the user with the press of a button. A prototype was built and featured in his book, but Brown was never able to acquire the capital to put his prototype into production.