1. Obby Oss Day, Padstow
Come and enjoy Padstow’s famous festival Obby Oss day, which falls on the first day of May (unless the 1st falls on a Sunday, then it is on the 2nd). Locals decorate the streets with bunting, flowers, flags, the maypole, and greenery. In the morning two “osses” are released from their stables, swirling and dancing they move through Padstow taunted by a Teazer, who leads the dance with theatrical movements. The accompanying people dance along to the drum, dressed in white and donning spring flowers. The festival ends with the followers of the “osses” singing a traditional May song.
www.padstow.com/obby_oss/obby_oss.php
2. Cornwall International Male Voice Choral Festival
This Festival is on once every two years, and attracts choirs from all over Europe including St Petersburg and the Czech Republic. The choirs will perform at venues all over Cornwall from the 2nd – 6th of May.
www.visitcornwall.com/whats-on/cornwall-international-male-voice-choral-festival 
3. English National Surfing Championships
Young surfers battle to knock established competitors off the top spot over three divisions. The competition takes place at Watergate Bay over 4th – 6th of May.
www.englishsurfing.co.uk 4. St Ives May Day
A celebration of spring, St Ives’ May Day tradition stretches over hundreds of years, and the town revived the festival several years ago. At noon, on the 6th of May, the Grand Bard and Mayor choose the May Queen and King and their attending Prince and Princess, in a ceremony known strangely as the “pee whip” The St Ives Guisers, dress in their traditional black and white "mock formal" make an appearance; horn blowers mark the start of spring.
At 1 pm there’s a parade to the harbour where you can watch May pole dances, traditional Cornish dancing and music. Various local choirs and brass bands perform by the harbour throughout the day, and throughout the May Day celebrations there’s a fish barbecue by the harbour.
5. Fowey Festival of Words and Music 
This diverse festival of literature, music, and performance has many exciting guest speakers, exhibitions, workshops, music and entertainment. The former Mayor of London, Ken Livingstone and War Horse writer Michael Morpurgo are both speakers. The festival runs from the 8th – 18th of May.
www.foweyfestival.com 6. Polo on the Beach The award-winning Veuve Clicquot Polo on the Beach event takes place once again at Watergate Bay, on the weekend of the 18th and 19th of May, featuring some of the country’s top professional polo players. It will be packed full of events, entertainment and music all on the beach.
www.watergatebay.co.uk/blog/2013/04/23/polo-on-the-beach-18th19th-may 7. St Ives Food and Drink Festival
This yummy festival takes place over the weekend of the 18th – 19th of May at St Ives and Porthminster Beach. Here Cornwall’s finest food and drink producers and chefs gather together to give you a taste of Cornwall that you’ll never forget.
www.stivesfoodanddrinkfestival.co.uk 8. Run to the Sun
This festival is one of the largest custom car, VW and dance festivals in Europe. Newquay’s original festival, Run to the Sun, has been going for over 20 years. This year will be the last one, so buckle your self in for a great weekend on the 24th – 27th of May.
www.runtothesun.co.uk 9. Fal River Festival
The Fal River Festival celebrates life up and down the Fal from the 24th of May – 2nd of June. The festival has events at various places and towns on the Fal river including food, music, walks, kayaking, readings and more.