Bohai Bay (simplified Chinese: 渤海湾; traditional Chinese: 渤海灣; pinyin: Bóhǎi Wān) is one of the three major bays of the Bohai Sea, the northwestern and innermost gulf of the Yellow Sea. It is bounded by the coastlines of eastern Hebei province (Tangshan and Cangzhou), Tianjin municipality and northern Shandong province (Binzhou and Dongying) south of the Daqing River estuary (which is an old mouth of Luan River in Laoting County) and north of the Yellow River estuary. It is the most southerly water in the Northern Hemisphere where sea ice can form.
The Bohai Bay is the drainage destination of the Hai River and 15 other rivers. Due to these rivers' muddy runoff, the bay used to be a highly silty water body, but extensive damming of the various river systems has greatly diminished siltage. Nevertheless, the Bohai Bay in effect concentrates the runoff of the whole eastern North China Plain, and the Bay is an intensely polluted body of water. Reduced silt deposition and sea level rise are causing problems with sea encroachment in some coastal areas.