Nakaumi 中海
Nakaumi 中海
Coordinates	35°28′N 133°12′E / 35.467°N 133.200°E / 35.467; 133.200
Type	Brackish
Primary inflows	Ohashi River
Primary outflows	Sakai Channel
Basin countries	Japan
Max. length	63.49 km (39.45 mi)
Max. width	22.8 km (14.2 mi)
Surface area	86.2 km2 (33.3 sq mi)
Max. depth	17.1 m (56 ft)
Water volume	0.47 km3 (380,000 acre⋅ft)
Shore length1	105 km (65 mi)
Surface elevation	0 m (0 ft)
Islands	Daikonjima, Eshima
Ramsar Wetland
Designated	8 November 2005
Reference no.	1551[1]
1 Shore length is not a well-defined measure.

Nakaumi (中海) is a brackish lake located between Tottori and Shimane prefectures in Japan. The lake is enclosed by the Shimane Peninsula to the north and Yumigahama Peninsula to the east. It is the fifth largest lake in surface area in Japan.

Nakaumi connects Lake Shinji (宍道湖 Shinji-ko) and the Sea of Japan, and is surrounded by the municipalities Matsue, Yasugi, Yonago and Sakaiminato.

There are two large islands in the lake, Daikon Island (大根島 Daikonjima, literally "radish island") and Eshima Island (江島 Eshima, "inlet island"). There are bridges (like the Eshima Ohashi Bridge) and roads that connect the east and west shores of the lake through the two islands.

Nakaumi is a brackish lake because it is connected to the Sea of Japan by a short channel, the Sakai Channel, and lies so low that the tides reverse the flow of the rivers all the way into Lake Shinji.

Nakaumi (中海) literally means "middle sea". Even though Nakaumi is a lake, it was likely named a sea because of its saline water and proximity to the actual sea. In Japanese, the lake is usually referred to simply as Nakaumi, not as Nakaumi-ko (Lake Nakaumi).^{[citation needed]}

• List of lakes in Japan