Tropical Storm Alpha was the 23rd tropical or subtropical storm of the extremely active 2005 Atlantic hurricane season. It developed from Tropical Depression Twenty-Five in the eastern Caribbean Sea on October 22, 2005. As the 21 pre-designated storm names had been exhausted, it was given the first name on the auxiliary list, which utilizes the letters of the Greek alphabet. This was the first hurricane season ever to trigger this naming protocol, and the only one until the 2020 season.

During its brief life, Alpha moved west-northwestward and reached its peak intensity on October 23, but weakened as it neared landfall in the Dominican Republic that same day. Crossing the island of Hispaniola it weakened to a tropical depression, and persisted until October 24, when it dissipated. Its remnant low was absorbed by Hurricane Wilma's large circulation.

Alpha dumped torrential rain on the island of Hispaniola, making it the eighth wettest storm to impact poverty-stricken Haiti. It caused 26 deaths, 17 of them in Haiti, and all of them caused by floods and rain-related landslides. Roads were blocked for weeks and hundreds of houses were destroyed.