Tropical cyclones in 2017

During 2017, tropical cyclones formed within seven different tropical cyclone basins, located within various parts of the Atlantic, Pacific and Indian Oceans. During the year, a total of 146 tropical cyclones had formed. 88 tropical cyclones had been named by either a Regional Specialized Meteorological Center (RSMC) or a Tropical Cyclone Warning Center (TCWC).

The most active basin in the year was the Western Pacific, which documented 27 named systems. However, the season was a slightly below-average season and the first since 1977 season saw no Category 5-equivalent super typhoon. The Eastern Pacific, despite amounting to 18 named systems, also was a was significantly less active than the previous three Pacific hurricane seasons (2014, 2015 and 2016). However, the North Atlantic hurricane featured 17 named storms, and was the costliest tropical cyclone season on record. It also had the fifth-most named storms since reliable records began in 1851 – tied with 1936 – and the most major hurricanes since 2005. The Australian region season experienced the average number of cyclones reaching tropical storm intensity, numbering 11, respectively. Activity across the southern hemisphere's three basins—South-West Indian, Australian, and South Pacific—was spread evenly, with each region recording seven named storms apiece. Three Category 5 tropical cyclones formed during the year. The accumulated cyclone energy (ACE) index for the 2017 (seven basins combined), as calculated by Colorado State University (CSU) was 621.1 units.

The strongest and deadliest tropical cyclone was Hurricane Maria with a minimum barometric pressure of 908 mbar (hPa; 26.81 inHg) and killing 3,000 people in Puerto Rico and Dominica. The costliest tropical cyclone of the year was Hurricane Harvey in the Atlantic, which struck Houston metropolitan area in August causing US$125 billion in damage, tying with Hurricane Katrina as the costliest tropical cyclone worldwide.