The traditional event dates back to the 12th century and sees the biggest gathering of the Gypsy, Romany and Traveller community in Europe.
Last year saw 10,000 travellers in the market town, with similar numbers expected this year.
Jim Price, Welsh Romany Gypsy
The fair includes the tradition of travellers washing their horses in the River Eden and showcasing their horse-drawn wagons.
With a large amount of animals around, event organisers and Cumbria Police have stressed the importance of keeping traffic under control.
They have warned all drivers going through the area to keep to a slow speed and take extra care around the site.
There is also a larger police presence around the town, with patrols happening regularly over the weekend.
The RSPCA are also out in force with 34 officers at the fair alongside other equine specialists.
Exhaustion of horses will be a big focus for the team this year.
Rob Malloy, RSPCA
“We’ve had overworked and dehydrated horses on our hands for the past three years.
The event runs until 9 June.