IPv6 now has something called ULA – Unique Local Addresses, described in RFC4193, which is not identical to RFC1918 IPv4 private addresses, but is very similar.
See this link for more information.
There doesn’t appear to be a private IP range with IPv6.
This is what I found online.
<pre>IPv6 does not include private network features such as NAT. Because of the very large number of IPv6 addresses (the IPv6 address space is 128 bits compared to 32 bits for IPv4), IPv6 users should be able to obtain IPv6 address space for use at their discretion and without artificial barriers between their network and the Internet. However, there is an address range allocated for cases where users will not be able to get an officially assigned network, namely the fc00::/7 range as described in RFC 4193. Addresses from this range are called “Unique Unicast”, since each network contains a 40 bit random number to prevent collisions when two private networks are interconnected.
A former standard proposed the use of so-called “site-local” addresses in the fec0::/10 range, but due to major concerns about scalability and the extremely fuzzy definition of “site”, its use has been deprecated since September 2004 in RFC 3879.</pre>
You can read up more on Private Networks segmengs here.