The company has also extended the range to include a new "Mini" model that has a smaller 5.4in screen.
The US firm bucked a wider industry downturn by increasing its handset sales over the past year.
But some experts say the new features give Apple its best opportunity for growth since 2014, when it revamped its line-up with the iPhone 6.
"5G will bring a new level of performance for downloads and uploads, higher quality video streaming, more responsive gaming, real-time interactivity and so much more," said chief executive Tim Cook.
There has also been a cosmetic refresh this time round, with the sides of the devices getting sharper, flatter edges.