The Sen Toku Class.
http://www.combinedfleet.com/sen_toku.htm

@ Ja:
The Regulus I was installed on two WW2 Gato/Balao class subs (2 missiles in a barrel behind the fin), redesignated as SSG, the first nuclear armed subs of the USN, plus in the late 1950s they built the two Grayback boats (4 missiles in a hangar over the bow), plus the one nuclear powered Hallibut (up to 5 missiles in an internal hangar in front of the fin). Hallibut was an interesting boat with a long life of special and covert missions.
USN fired over 100 Regulus I (incl from cruisers and carriers). From 1959 to 1964 (incl Cuban Crises) these five boats were the only nuclear armed boats of the USN. That was before Polaris.
Funny story: In 1959 the USN tried rapid-mail delivery with Regulus.

And then there was SSM-N-6 Rigel, but that was never launched from a boat.