Robert McMillan may refer to:
- Robert S. McMillan (architect) (1916–2001), architect and co-founder of The Architects Collaborative
- Robert S. McMillan (astronomer), astronomer at the University of Arizona
- Robert McMillan (Australian judge) (1858–1931), Chief Justice of the Supreme Court of Western Australia
- Robert Johnston McMillan (1885–1941), U.S. federal judge
- Robert Thomas McMillan (1887–1962), member of the New Zealand Legislative Council
- Robert MacMillan (1865–1936), Scottish national rugby union player
- Bob MacMillan (born 1952), Canadian hockey player and politician