Thaddeus S. Lowe observing the battle from his balloon "Intrepid".

Thaddeus S. Lowe (1832–1913) was an American aeronaut, scientist, and inventor known for his pioneering work in military ballooning during the American Civil War. Born in New Hampshire, he became a self-taught balloonist and developed advanced hydrogen balloons.

During the Civil War, Lowe convinced President Abraham Lincoln of the strategic value of aerial reconnaissance. He became the chief aeronaut of the Union Army Balloon Corps, using balloons to gather intelligence on Confederate troop movements. His efforts significantly contributed to early military aviation.

After the war, Lowe pursued various scientific and business ventures, including innovations in gas manufacturing and rail transport. He later moved to California, where he developed an early mountain railway. He died in 1913, leaving a legacy in aviation and engineering.