Dennis Albert Blakeslee (March 11, 1856 – April 5, 1933) was an American politician who was the 74th Lieutenant Governor of Connecticut from 1911 to 1913.

At the age of sixteen he began working for his father, a contractor, as a time keeper.

He continued on with the company in Bridgeport and was in partnership with his father and his brother, Clarence, becoming a very successful contractor with particular emphasis on railroad construction.

He served eight years in the Second Company of the Governor's Horse Guard, part of the time as Major in command of the organization.

His service was under Democratic Governor, Simeon E. Baldwin, during whose tenure, a public utilities commission was founded, and a workmen's compensation bill was enacted, the Corrupt Practices Act, and a civil service law was passed.