A ballpoint pen, also known as a biro (British English), ball pen (Bangladeshi, Hong Kong, Indian, Indonesian, Pakistani, Japanese and Philippine English), or dot pen (Nepali English and South Asian English), is a pen that dispenses ink (usually in paste form) over a metal ball at its point, i.e., over a "ball point". The metals commonly used are steel, brass, or tungsten carbide. The design was conceived and developed as a cleaner and more reliable alternative to dip pens and fountain pens, and it is now the world's most-used writing instrument; millions are manufactured and sold daily. It has influenced art and graphic design and spawned an artwork genre.

The concept of using a "ball point" within a writing instrument to apply ink to paper has existed since the late 19th century. In these inventions, the ink was placed in a thin tube whose end was blocked by a tiny ball, held so that it could not slip into the tube or fall out of the pen.

The first patent for a ballpoint pen was issued on 30 October 1888 to John J. Loud, who was attempting to make a writing instrument that would be able to write "on rough surfaces—such as wood, coarse wrapping paper, and other articles" which fountain pens could not. Loud's pen had a small rotating steel ball held in place by a socket. Although it could be used to mark rough surfaces such as leather, as Loud intended, it proved too coarse for letter-writing. With no commercial viability, its potential went unexploited, and the patent eventually lapsed.

The manufacture of economical, reliable ballpoint pens as are known today arose from experimentation, modern chemistry, and the precision manufacturing capabilities of the early 20th century. Patents filed worldwide during early development are testaments to failed attempts at making the pens commercially viable and widely available. Early ballpoints did not deliver the ink evenly; overflow and clogging were among the obstacles faced by early inventors^[who?]. If the ball socket were too tight or the ink too thick, it would not reach the paper. If the socket were too loose or the ink too thin, the pen would leak, or the ink would smear. Ink reservoirs pressurized by a piston, spring, capillary action, and gravity would all serve as solutions to ink-delivery and flow problems.

László Bíró, a Hungarian newspaper editor (later a naturalized Argentine) frustrated by the amount of time that he wasted filling up fountain pens and cleaning up smudged pages, noticed that inks used in newspaper printing dried quickly, leaving the paper dry and smudge-free. He decided to create a pen using the same type of ink. Bíró enlisted the help of his brother György, a dentist with useful knowledge of chemistry, to develop viscous ink formulae for new ballpoint designs.

Bíró's innovation successfully coupled viscous ink with a ball-and-socket mechanism that allowed controlled flow while preventing ink from drying inside the reservoir. Bíró filed for a British patent on 15 June 1938.

In 1941, the Bíró brothers and a friend, Juan Jorge Meyne, fled Germany and moved to Argentina, where they formed "Bíró Pens of Argentina" and filed a new patent in 1943. Their pen was sold in Argentina as the "Birome", from the names Bíró and Meyne, which is how ballpoint pens are still known in that country. This new design was licensed by the British engineer Frederick George Miles and manufactured by his company Miles Aircraft, to be used by Royal Air Force aircrew as the "Biro". Ballpoint pens were found to be more versatile than fountain pens, especially in airplanes, where fountain pens were prone to leak.

Bíró's patent, and other early patents on ballpoint pens, often used the term "ball-point fountain pen".^{[self-published source?]}