The new 5C was billed as a handset that will be "more fun and more colourful" than any iPhone yet at a much-hyped event at Apple's California headquarters.
Chief executive Tim Cook promised the gadget would come with "all the great technology customers have loved with the iPhone 5".
The mobile will come in five colours - blue, white, pink, yellow, and green - and will be priced at $99 (£63) if taken out on a two-year contract. The cheaper version of the iPhone will be an obvious rival to some of the low-cost gadgets sold by competitors.
Mr Cook also introduced new flagship mobile, the iPhone 5S, "the most forward-thinking phone we have ever created".
Dubbed the "gold standard in smartphones" by the tech giant, it will come in the more traditional Apple colours as well as a new golden hue.
Its unveiling comes after a series of images leaked online claimed to show the 5S, while the industry was awash with rumours relating to the 5C. Mr Cook raised a laugh as he told the audience: "A couple of you may have been expecting this."
Apple's Philip Schiller raised a massive round of applause as he introduced the fingertip scanner -named Touch ID - which, he said, would provide a "simple and secure way to unlock your phone with just a touch of your finger."
The security feature is built into the home button.
Beyond unlocking the phone, the feature can be used as a secure way to approve purchases from the iTunes Store, App Store or iBooks Store, Apple said.
The 5S will cost from £549.