The new lower rate, down from 7.6% APR, will be available online or via the phone (0800 028 4055 quoting 7030) until midnight on Wednesday 28 August.
It will effectively reduce the cost of a £20,000 loan over five years by over £424(1).
This will be the first in a series of special offers on personal loans from Santander, with more deals to be announced in the coming weeks.
Nick Potter, head of personal loans at Santander, said: "As the economic environment begins to improve people feel more confident about borrowing, and Santander is increasing its lending accordingly.
"Whether it's for a car, home improvements or the holiday of a lifetime, a personal loan can be a cost-effective way to borrow, especially with rates being so competitive right now."
