Ladislao "Laszlo" Josef Biro (Bíró László József, September 19, 1899 - November 24, 1985) is considered the inventor of the modern ballpoint pen.

Biro was born in Budapest in 1899. In 1938, while working as a journalist, he noticed that the ink used in newspaper printing dried quickly, leaving the paper dry and smudge-free. He tried using the same ink in a fountain pen but found that it would not flow into the nib, as it was too viscous. Working with his brother Georg, a chemist, he developed a new tip consisting of a ball that was free to turn in a socket, and as it turned it would pick up ink from a cartridge and then roll to deposit it on the paper. Biro patented the invention in Paris in 1938, after fleeing anti-Jewish laws in Hungary.

In 1943 the brothers moved to Argentina and on June 10 filed another patent, and formed Biro Pens of Argentina. This new design was licensed by the British, who produced ballpoint pens for Royal Air Force aircrew, who found they worked much better than fountain pens at high altitude.

Ballpoint pens are still widely referred to as a biro in many countries, notably several European countries, Australia and New Zealand. Argentina's Inventors Day is celebrated on Biro's birthday, September 19.