European internet address allocator the Ripe Network Co-ordination Centre (RIPE NCC) has started distributing its last blocks of IPv4 address.
Those applying will only receive an allocation if they have a demonstrable need and have enacted plans to migrate to IPv6.
"We've known for many years that this moment would eventually come," RIPE NCC managing director Axel Pawlik in a blog post.
"It's the end of an era, and also the beginning of the next stage in Internet history."
IPv4 is the fourth version of the internet protocol (IP) that allows systems to network. It is the most widely used IP for assigning numerical values to internet capable devices and services.
The main problem with IPv4 is that it uses a 32-bit long structure for its internet addresses.
Its limited address length means that available addresses using IPv4 will max out at 4.29bn. The influx of new devices and a constantly growing web user base has meant that a replacement for IPv4 is needed.
IPv6 was created to ease the address crunch. The protocol was created using a 128-bit addresses structure which puts available internet addresses at an almost infinite number.
IPv4 is not forward compatible so ISPs and router vendors would have to actively enable IPv6 on all products and services. The finances and manpower required for the switch has made it difficult to convince people to make the upgrade.
Demand for the switch to IPv6 has been around for years. As far back as 2010 analysts were reporting IPv4 addresses could run out within the year.
Recently, major companies have been attempting to prove the need for IPv6. Last June companies like Facebook began promoting IPv6 World Launch Day as means to spread the word.