Miss Universe 2009 was the 58th Miss Universe pageant, held at the Imperial Ballroom in Atlantis Paradise Island, Nassau, the Bahamas, on August 23, 2009.

At the end of the event, Dayana Mendoza of Venezuela crowned Stefanía Fernández of Venezuela as Miss Universe 2009. This marks the first time in Miss Universe history that a country has won twice consecutively.

Contestants from 83 countries and territories competed in this year's pageant. The competition was hosted by Billy Bush and Claudia Jordan; Bush last served as host during Miss Universe 2005. Heidi Montag, Flo Rida, Kelly Rowland, and David Guetta performed in this year's pageant.

The competition also featured the debut of the new Diamond Nexus Crown. For the first time ever, fans are able to vote between three designs for the new crown. The fans voted for the Peace crown, which is set with 1,371 gemstones, weighing a total of 416.09 carats or 83.218 g. It is made with an alloy that contains 544.31 grams of 14k and 18k white gold as well as platinum. The crown also featured synthetic rubies to represent the main advocacy of Miss Universe which is HIV/AIDS education and awareness. It is considered to be an eco-friendly crown due to its synthetic stone materials.

Donald Trump, president of the Miss Universe Organization, had intentions on holding the 2009 pageant in Dubai. However, the negotiations did not materialize due to the political instability regarding relations between the United Arab Emirates and Israel and also for religious reasons. Croatia was also interested in hosting the 2009 pageant. However, the country withdrew its bid to host the contest due to economic problems related to the current global economic crisis.

On July 1, 2008, investor Jonathan Westbrook tried launched a bid for Australia to host the 2009 edition of the pageant. However, his efforts were in vain as the possible venues were not interested. Eventually, on March 3, 2009, the Miss Universe Organization announced that the competition would be at the Atlantis Paradise Island in Nassau, The Bahamas. The pageant would initially take place on August 25, however, the contest was moved to August 23, 2009.

Contestants from eighty-three countries and territories were selected to compete in the competition. Four of these delegates were appointees to their positions after being a runner-up of their national pageant or being selected through a casting process, while another was selected to replace the original dethroned winner.

Angenie Simon, the first runner-up of Miss Curaçao 2009, was appointed to represent Curaçao after Ashanta Macauly, Miss Curaçao 2009, withdrew due to unknown health problems. Bélgica Suárez, the runner-up of Miss Honduras 2008, was appointed to represent Honduras at Miss Universe due to the political crisis in Honduras. Võ Hoàng Yến, the first runner-up of Miss Universe Vietnam 2008, was appointed as Miss Universe Vietnam 2009 by UNICorp, the franchise holder of Miss Universe in Vietnam.