IPv6
The successor to IPv4 — 128-bit addresses and 340 sextillion addresses.
Looks like 2001:0db8:85a3:0000:0000:8a2e:0370:7334 (compressed to 2001:db8:85a3::8a2e:370:7334). Enough for every grain of sand on Earth to have its own IP.
Designed in 1998. Migration is still ongoing — Sweden hovers around 30% IPv6 traffic. NAT kept IPv4 viable longer than anyone expected.