World Horizontal Directional Drilling Day, also known as World Trenchless Technology Day, is observed worldwide on every fourth Thursday of September. Established in 2016 during a seminar by the International Association of Horizontal Directional Drilling Specialists, this day highlights the industrial, technical, economic, and socio-environmental benefits of horizontal directional drilling (HDD). HDD, invented by Martin Cherrington in the early 1960s, is a trenchless method for installing underground utilities that minimizes surface disturbance and is particularly useful in environmentally sensitive or congested areas. The day serves as a professional holiday for HDD specialists, emphasizing their role in a technologically advanced segment of the construction industry. The International Organization of HDD Specialists, founded in 2002 by 17 enterprises from five countries, plays a significant role in promoting this observance.