Guiuan is a 3rd class municipality in the province of Eastern Samar, Philippines. As of year 2004, it has a population of 43,647 people in 7,618 households.

Guiuan is a significant part of the Philippine history. In the 16th century, when Ferdinand Magellan discovered the Philippines, it is believed that he first landed on the island of Homonhon. It is probably because of this fact that the majority of the population of the town are devout Catholics and the town's church, the Church of the Immaculate Conception, is one of the oldest in the country.

During the Second World War, Guiuan served as one of the Alliance's bases. What's left of the American occupation nowadays are just concrete slabs which once served as the foundations of a vast supply depot, and an air strip which now serves as the town's own airport.