Statue of Petar II Petrović Njegoš

Petar II Petrovic Njegos, last Prince-Bishop of Montenegro

I believe this statue commemorate Peter II, nephew of Peter I.
If so, he would formally be known as Petar II Perovic Njegos - usually known simply as Njegos [Nye-gosh].
Unlike Peter I who reigned for 48 years, Peter II had a comparatively short reign, since he died at the young age of 37.
Apart from ruling the territory of Montenegro, Peter II (Njegos) was a very well-known and highly regarded philosopher and writer. His works are still consider important both in the Serbo-Croatian canon and more widerly to this day. Like Peter I, Peter II was Prince-Bishop of Montengro - having committed to a celibate monastic life, the succession line was uncle to nephew. Peter II's nephew Danilo renounced this, transferring spiritual power to the Metropolitan (Bishop in Orthodox church) and assuming only corporal power as Prince.