Allister Grosart, PC (December 13, 1906 – February 8, 1984) was a Progressive Conservative politician, Senator, journalist and businessman in Canada.
During World War II, he served with the 2nd battalion of the Irish Regiment reaching the rank of major.
He was also a key organizer in the subsequent 1958 election in which the Diefenbaker government was returned with the largest majority in Canadian history.
He served as deputy leader of the Opposition from 1974 until 1979, and became Speaker of the Senate of Canada when the Tories again formed government from 1979 to 1980 under Joe Clark.
Grosart retired from the Senate in 1981, and was appointed to the Queen's Privy Council for Canada in honour of his long service.