Thomas C. MacMillan (October 4, 1850 – December 13, 1935) was a Scottish American politician, Congregationalist, and newspaper reporter from Wigtownshire, Scotland.

He served eight years in the Illinois General Assembly and was active in church affairs.

He was part of the committee that wrote the Chicago Sanitary District Act of 1889 and advocated for its passage.

MacMillan was also a member of the senate committee on the World's Columbian Exposition, which authorized a $80,000 grant for the fair.

[2] He died at his home in La Grange on December 13, 1935, and was buried at Na-Au-Say Cemetery in Yorkville.