The 2009 Southeast Asian Games (Lao: ກີລາພູມິພາກອາຊີຕາເວັນອອກສຽງໃຕ້ 2009, translit. Kila phoumipak asi taven oak siang tai 2009), officially known as the 25th Southeast Asian Games, were a Southeast Asian multi-sport event hosted by Vientiane, Laos. This was the first time Laos had held the Southeast Asian Games as Laos had previously declined hosting the 1965 Southeast Asian Peninsular Games, citing financial difficulties. This was also the first time the Southeast Asian Games was held in a landlocked country.

The games commemorated 50 years of SEA Games and the main schedule was formally held from 9 to 18 December 2009, with several events had commenced from 2 December 2009. Around 3,100 athletes participated at the event, which featured 372 events in 25 sports. Laos is the ninth nation to host the games after Thailand, Myanmar, Malaysia, Singapore, Indonesia, Philippines, Brunei and Vietnam. It was opened by Choummaly Sayasone, the President of Laos at the New Laos National Stadium.

The final medal tally was led by Thailand, followed by Vietnam and Indonesia with host Laos in seventh place. Several Games and national records were broken during the games.

During the Southeast Asian Games Federation meeting at the 2003 Southeast Asian Games in Vietnam, Vientiane, the capital city of Laos was chosen as the host of the 2009 Southeast Asian Games.

The Laos 25th SEA Games Organising Committee (LAOSOC) led by president Somsavath Lengsavath was formed to oversee the staging of the games.

The logo of the 2009 Southeast Asian Games is the image of the Pha That Luang, the national landmark and shrine of Laos beside the Mekong River. The shrine represents Laos as the host of the 2009 Southeast Asian Games and the Lao Culture, Arts and History, whereas the Mekong River, resembled by three wavy lines below the shrine, represents the origin of life, culture and lifestyle of Lao community especially in sports. The river itself also represents the integration of the Southeast Asian countries and the friendship made through sport events.

The mascots of the 2009 Southeast Asian Games are two white elephants dressed in traditional Lao attire named Champa and Champi. Champa is the male elephant and Champi is the female elephant. The elephants symbolises the host nation, Laos as it was known as the kingdom of Lan Xang in ancient times, which literally means "the kingdom of a million elephants". The cheerful expression on the faces of the mascots represents the joyful and lively atmosphere during the games and warm welcome from Laos as the host country of the 25th SEA Games.

33 songs were written for the games, which included The Spirit of the Flame, the theme song of the games which was written and performed by Sam Intharaphithak. Other songs included "Go Laos" which was sung by Sam Intharaphithak, Nalin Daravong, and Kave, "SEA Games Harmony" which was sung by Sithiphone, Sam Intharaphithak, Gai, Malya and Poui and "Vientiane Games" which was sung by Buratino. A Beerlao Campaign song for the games was also composed.