Alejandro Salmero Melchor Sr. (August 9, 1900 – September 5, 1947) was a Filipino civil engineer, mathematician, educator and member of the Cabinet of the Philippines. A native of Ibajay, Aklan, Melchor was also known for his work on pontoon bridges during the Second World War.
The historic Melchor Hall in the University of the Philippines Diliman campus is named after him. The hall houses most of the units of the UP College of Engineering. A building in the Philippine Military Academy was also named in his honor.