Riyadh said it would give Canada's ambassador 24 hours to leave the country and that it would also withdraw its envoy to Ottawa.
The Canadian embassy in Riyadh had said it was "gravely concerned" about a new wave of detentions of human-rights campaigners in the kingdom, including Samar Badawi, an award-winning gender rights activist.
The Saudi foreign ministry slammed the Canadian statement, signalling its growing irritation over Western criticism of the kingdom's poor human rights record.
"It is quite unfortunate to see the phrase "immediate release" in the Canadian statement, which is a reprehensible and unacceptable use of language between sovereign states".
Both campaigned for women's right to drive, which was granted by the Saudi government when it ended a decades-old ban in June, as well as the abolishment of the male guardianship system.
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The Saudi ministry described Canada's criticism of the arrests as "blatant interference in the kingdom's domestic affairs, against basic global norms and all worldwide protocols" and a "major, unacceptable affront to the kingdom's laws and judicial process, as well as a violation of the kingdom's sovereignty".
Human Rights Watch has called the arrests "an unrelenting crackdown on the women's rights movement". His wife, Ensaf Haidar, and their three children became Canadian citizens on Canada Day last month and live in Quebec.
Bilateral trade past year totalled about $4bn and more than 15,000 Saudi students attend Canadian universities.
The decision has been reported by Saudi Arabia's official Saudi Press Agency.
In April, Canadian Prime Minister Justin Trudeau expressed his "serious concern" over the continued jailing of Badawi to King Salman.
Riyadh's expulsion of the Canadian ambassador was meant to send a strong message to other critical Western governments, observers say.
The move is the first since the two countries broke off diplomatic ties in 2016, after Iran allowed protestors to attack and burn the Saudi embassy in Tehran.