The new device is slimmer, lighter, faster and more powerful than the previous model, the computing giant announced.
It weighs 1lb, compared to 1.4lb of the iPad 4, and is 7.5mm thin compared to 9.4mm - making it 20% thinner.
There is also 43% smaller bezel around the edge of the screen.
The iPad Air will be available on November 1 in the UK and many other countries around the world.
Apple also unveiled a new iPad mini with a retina display, which will be available later in November.
They will both come in silver/white and grey/black versions.
Speaking at the Yerba Buena Centre in San Francisco, Apple CEO Tim Cook said: "I couldn't be prouder of both new iPads."
He said he could not think of another product that had come so far, so fast, adding: "We want to help our customers create even more amazing stories, because we know this is just the beginning for iPad, and so we've been busy working on the next generation of iPad."
Phil Schiller, senior vice president of worldwide marketing described it as a "screaming fast iPad", with faster graphics and wifi access.
He described the iPad Air as "a whole new generation" and added: "This is probably our biggest leap forward."
The iPad Air will cost from £399, including VAT, the price for the 16GB WiFi model.
The price increases to £479 for the 32GB model, £559 for 64GB and £639 for 128GB.
The WiFi Cellular versions will be £100 more expensive in each case.
It will be the lightest full-sized tablet in the world, according to Apple.
"When you hold it, it will be a dramatically different experience," said Mr Schiller.
He said every possible hundredth of an inch had been shaved off to make it so thin.
"To make an iPad this thin took a huge amount of work, over years," he added. "The first time you pick it up and feel it yourself, you will understand why we're so excited about it."
It has a 9.7 inch retina display and an A7 chip inside, with over a billion transistors.
It offers a twofold increase in rendering, is twice as fast at opening files and has double the graphics performance of the iPad 4.
Other key features include a new FaceTime HD camera and dual microphones.
The iPad Air will have the same 10-hour battery life as its predecessor.
The new iPad mini costs from £319, for the WiFi 16GB version, rising to £399 for 32GB, £479 for 64GB and £559 for 128GB.
Again, the cost for the WiFi cellular version is £100 extra in each case.
The new version of the iPad mini has the same 2048x1536 pixels of the iPad Air and the same apps will run on each. It is also powered by the A7 chip, which Mr Schiller described as "a big jump in performance".
It will be up to four times faster at graphics than the first generation model. It will also have double the WiFi speed and expanded support for broadband wireless networks, like the iPad Air.
The cost of the original iPad mini has been lowered to a starting price of £249 for the 16GB version, with the cost £349 for the WiFi cellular model.
Mr Schiller said this was the lowest price ever.
The iPad 2 will now cost £329 for WiFi with 16GB, and £429 with 3G.
A range of new covers and cases for…