The new iPhones could be reserved through the website and Apple Store app starting at 12:01am PT or 3:01am ET in the US, and 8:01am BT in the UK. The actual iPhone 6S release date is September 25.
New to this year's configuration is a rose gold iPhone 6S color and 6S Plus color choice, in addition to the usual gold, space gray and silver shades of aluminum.
iPhone 6S website and app down
Apple's official website to buy the iPhone 6S and iPhone 6S Plus was down ahead of today's pre-order rollout, and that's customary in advance of any big product launch from the company.
However, some prospective buyers weren't able to access the Apple Store site right away, leading to a delays in purchasing the highly-sought-after phones.
Others, according to Twitter, tend to find better luck using the free Apple Store mobile app. In past years, we've found that it worked up to a half hour sooner than the website through a computer browser.
Considering all of the hype surrounding the rose gold iPhone, this may leave some Apple fans without the exact iPhone 6S they were wanting on day one.
Shipping time often get delayed minutes after new Apple products go on sale, and although this is an "S" phone, demand is still expected to be high for launch day.