The Aranmula Uthrittathi Vallamkali, or Aranmula Boat Race, is one of the oldest and most revered boat races in Kerala. Held on the day of the Uthrittathi asterism in the Malayalam month of Chingam (which falls between 15 August and 20 September), this event is known for its grandeur and rich history. The race takes place on the serene waters of the Pamba River in Pathanamthitta district, drawing thousands of spectators and participants every year.

Aranmula is a heritage village situated along the banks of the Pamba River. According to legend, a devout Brahmin once vowed to provide all the essentials for the Thiruvona Sadya (a feast held on the Thiruvonam asterism) at the Aranmula Sree Parthasarathy Temple. These provisions were to be delivered in a boat known as the Thiruvona Thoni. During the journey, the boat was attacked by enemies, but snake boats from nearby areas came to its rescue. This act of bravery and unity is said to have given rise to the tradition of the Aranmula Boat Race. The race itself is an offering to Lord Krishna, the presiding deity of the Sree Parthasarathy Temple.

The boats used in this race are called Palliyodams, and their design is attributed to Lord Krishna. According to local lore, Lord Krishna appeared on the banks of Aranmula on a raft made of six bamboos, which is how the village got its name—Aranmula, meaning "six bamboos." These Palliyodams are larger and taller than the typical snake boats used in other parts of Kerala. They can accommodate up to 15 people standing in the center, making them a sight to behold during the race.

The Aranmula Boat Race is deeply intertwined with the rituals and religious practices of the Aranmula Parthasarathy Temple. The race is held annually on Uthrittathi in the month of Chingam, which is also the anniversary of the idol's dedication at the temple. Legend has it that the goddess Bhumi Devi re-dedicated the idol in Aranmula from Nilakkal, where Arjuna had initially installed it. The boat race is believed to be blessed by divine presence, adding a spiritual dimension to the event.

Another legend associated with the race involves Lord Krishna appearing in the dream of the Bhattathiri of Kattoor Mangadu Illam, asking him to provide a feast to the Aranmula temple on every Thiruvonam day. This tradition continued for years until one day, the Bhattathiri's boat was attacked by bandits. The local people, upon learning of the attack, came to his aid on their boats, protecting the Thiruvona Thoni and Bhattathiri. This event is commemorated annually with the water procession and boat race.

The Aranmula chundan boats, known as Palliyodams, are unique in their design and structure. They are categorized into A and B grades for the competitions. The oarsmen sing traditional boat songs known as Vanchippattu, with Aranmula having its own specific songs such as Kuchelavritham, Bheeshmaparvam, and Santhanagopalam. The rhythmic rowing and singing, combined with the visual spectacle of the beautifully adorned boats, create a mesmerizing experience for the spectators.

The Aranmula Boat Race is not just a sporting event but a cultural and religious celebration that showcases Kerala's rich heritage. The event attracts thousands of tourists, both domestic and international, who come to witness this unique festival. The race is part of the larger Onam celebrations, making it a significant event in Kerala's festival calendar. The entire village of Aranmula and the banks of the Pamba River come alive with festivities, embodying the spirit of unity and tradition that defines this historic boat race.