The charity hopes the ring, called The Pinkie, will raise awareness of its work on breast cancer in the run-up to Breast Cancer Awareness month in October.
The introduction of the ring format follows the charity's use of a pink breast cancer ribbon last year. It intends to create a symbol that will differentiate it from other organisations.
The Pinkie is made from a similar material to the wristbands and will be available from Cancer Research UK shops in packs of three for £1. The multi-pack is designed to be shared among friends.
Each Pinkie is engraved with the message 'All women together', highlighting Cancer Research UK's campaign to raise awareness of the disease that killed 12,696 women in the UK in 2003.
Celebrities backing The Pinkie include singer Jenny Frost and actress Fay Ripley.