Marson Blair Hull, Jr. (born September 3, 1942), commonly known as Blair Hull, is an American businessman and politician, notable for his attempt to win the Democratic Party nomination to serve in the United States Senate from Illinois in 2004. He was also founder and chief executive officer of the Hull Group, a securities brokerage firm that was sold to Goldman Sachs.

In early media polls leading up to the March 16, 2004 primary election, Hull enjoyed a substantial lead and widespread name recognition resulting from a well-financed advertisement effort. He contributed over $28 million of his personal wealth for the campaign. When allegations surfaced of abuse against his ex-wife, Hull's poll numbers dropped and he failed to win the nomination. Illinois State Senator Barack Obama later became the nominee.