National Ballpoint Pen Day is observed worldwide every June 10, celebrating the invention of the modern ballpoint pen by the Bíró brothers, László and György, who filed a patent for their creation in Argentina. The ballpoint pen, which dispenses ink through a metal ball at its tip, was developed as a cleaner and more reliable alternative to fountain pens. The concept of a ballpoint pen dates back to the late 19th century, with an early design by American inventor John J. Loud in 1888, but it was the Bíró brothers who successfully created a commercially viable version. Their invention was first showcased at the Budapest International Fair in 1931, and they later filed a new patent on June 10, 1943, after fleeing Europe during World War II. The ballpoint pen gained popularity, especially after being used by the Royal Air Force due to its practicality in airplanes. Today, it is the most widely used writing instrument, making this holiday a fitting tribute to its significance in everyday life.