Robert William (Bob) Mattson Sr. (August 26, 1924 – March 14, 1982) was an American army veteran, lawyer, and politician in Minnesota, where he was the state Attorney General from 1964 to 1967.

Mattson attended public schools in the Minnesota Iron Range city of Virginia, where he was born in 1924.

Upon return to his home town, Mattson was active in the Disabled American Veterans and was named first commander of the local chapter.

Mattson attended Carleton College and was a graduate of the University of Minnesota Law School.

In 1964, Mattson was appointed Attorney General by Governor Karl F. Rolvaag to fill the remaining two years of Walter F. Mondale's term upon Mondale's appointment to the U.S. Senate to fill the vacancy created by Hubert H. Humphrey's election as Vice President of the United States.