Timeline of the 2021 Atlantic hurricane season

The 2021 Atlantic hurricane season was the third most active Atlantic hurricane season on record with 21 named storms, and the sixth consecutive year in which there was above-average tropical cyclone activity The season officially began on June 1, 2021, and ended on November 30, 2021. These dates, adopted by convention, historically describe the period in each year when most Northern Atlantic tropical cyclones form. However, tropical cyclone formation is possible at any time of the year, as was the case this season, when Tropical Storm Ana formed on May 22. The season's final system, Tropical Storm Wanda, dissipated on November 7.

Of the season's 21 named storms, seven became hurricanes, and four further intensified into major hurricanes. The season's most devastating storm was Hurricane Ida. It made landfall in Louisiana with maximum sustained winds of 150 mph (240 km/h), destroying coastal communities in its path.

This timeline documents tropical cyclone formations, strengthening, weakening, landfalls, extratropical transitions, and dissipations during the season. It includes information that was not released throughout the season, meaning that data from post-storm reviews by the National Hurricane Center, such as a storm that was not initially warned upon, has been included.

The time stamp for each event is first stated using Coordinated Universal Time (UTC), the 24-hour clock where 00:00 = midnight UTC. The NHC uses both UTC and the time zone where the center of the tropical cyclone is currently located. The time zones utilized (east to west) are: Greenwich, Cape Verde, Atlantic, Eastern, and Central. In this timeline, the respective area time is included in parentheses. Additionally, figures for maximum sustained winds and position estimates are rounded to the nearest 5 units (miles, or kilometers), following National Hurricane Center practice. Direct wind observations are rounded to the nearest whole number. Atmospheric pressures are listed to the nearest millibar and nearest hundredth of an inch of mercury.