It borders Sơn La, Hòa Bình, and Ninh Bình to the north, Nghệ An to the south, the Laotian province of Houaphanh to the west with a boundary of over 192 kilometres (119 mi) long, and the South China Sea (Gulf of Tonkin) to the east.

Thanh Hóa is a relatively large province; it ranks fifth in area and third in population among 63 central administrative subdivisions.

Human civilization has existed in Thanh Hóa since about 6,000 years ago and was one of the earliest centers of the ancient Vietnamese.

Thanh Hóa has two provincial cities, one district-level town and 24 rural districts with an area of 11,114.71 km2 (4,291.41 sq mi),[1] and a population of approximately 3.6 million.

Nghi Sơn is a promising economic zone, expected to become the centre of Thanh Hoa's industry with a large refinery factory, deepwater seaport, and many projects in progress.