Penzhina Bay (Russian: Пе́нжинская губа́, Penzhinskaya guba), also Penzhin, Penzhinsk or Penzhinskaya Bay, Gulf or Sound, is a long and narrow bay off the northwestern coast of Kamchatka, Russia.
Penzhina Bay is an upper right arm of Shelikhov Bay in the NE corner of the Sea of Okhotsk. It is bounded on the east by the Kamchatka Peninsula and on the west by the Taygonos Peninsula which separates it from Gizhigin Bay. It is about 300 km long and 65 km wide. Near the middle two peninsulas narrow it to 30 km. It freezes from October to May. It has the highest tides of any bay on the Pacific Ocean (9 meters, 12.9m maximum, versus 17 meters in the Bay of Fundy). Its basin is very thinly populated.
The Penzhina River flows into the head of the bay. It is 713 km long and flows east, then south, then southwest to reach the bay. The town of Penzhina was on the middle Penzhina and was visited by George Kennan in 1866. The major tributary of the Penzhina is the Aklan, Oklan or Khayakha River which flows southeast and joins the Penzhina about 50 miles from its mouth. In 1669 the Russians built the ostrog of Aklansk, which was used to subdue the local Koryaks and was an important base on the route south from Anadyrsk to the Kamchatka peninsula before the sea route from Okhotsk opened up. It was attacked by the Koryaks several times and later abandoned.