This timeline documents all of the events of the 2009 Pacific typhoon season which was the period that tropical cyclones formed in the Western Pacific Ocean during 2009, with most of the tropical cyclones forming between May and November. The scope of this article is limited to the Pacific Ocean, north of the equator between 100°E and the International Date Line. Tropical storms that form in the entire Western Pacific basin are assigned a name by the Japan Meteorological Agency. Tropical depressions that form in this basin are given a number with a "W" suffix by the United States' Joint Typhoon Warning Center. In addition, the Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA) assigns names to tropical cyclones that enter or form in the Philippine area of responsibility. These names, however, are not in common use outside of the Philippines.

The 2009 Pacific typhoon season was a below average season that spawned only 22 named storms, 13 typhoons, and five super typhoons. It was also recognized as the deadliest season in the Philippines for decades. The first half of the season was very quiet whereas the second half of the season was extremely active. The season's first named storm, Kujira, developed on May 3 while the season's last named storm, Nida, dissipated on December 3.