Lawyers for both the plaintiffs and provincial government had urged Ontario Superior Court Justice Barbara Conway to approve the deal, which also includes a formal apology from the premier.
"While more is always better, it is a compromise," Conway said.
"The settlements are fair, reasonable and in the best interests of the class members."
The deal reached in December calls for a minimum payment of $2,000 to members of the class and a maximum of $35,000.
Retired Supreme Court of Canada justice Ian Binney would review the more complex claims.
The class actions were launched on behalf of about 4,300 former residents of the Rideau Regional Centre in Smiths Falls, Ont., which opened in 1951, and the Southwestern Regional Centre near Chatham, Ont., which opened in 1961.
The purpose of the institutions was to house people labelled "retarded." The thinking was that residents — most of whom began living at the facilities as children — were better off than living with their families.
However, many of the thousands of residents suffered physical and sexual abuse at the overcrowded and understaffed prison-like institutions.
"I have suffered to this day," former Rideau resident Doug Smith told the court.
"It kind of ruined my life a little bit. It's very painful."
Government ministers and their deputies were made aware of the poor conditions but complaints fell on deaf ears, court heard.
"Many thousands of people suffered harm for no reason," lawyer Kirk Baert, speaking for the complainants, told the court.
"None of these people had done anything wrong. None of them deserved this treatment."
The proposed settlement is similar to a $32.7-million deal reached last year over the Huronia Regional Centre in Orillia, Ont.
Premier Kathleen Wynne formally apologized for the pain and loss that permanently marked hundreds of former residents of the now-shuttered Huronia facility.
Under the new agreement, Wynne will also formally apologize to those sent to Rideau and Southwestern, said Robert Ratcliffe, a lawyer for the province.
The apology is a "vital and extraordinary" component of the settlement, Conway said.
Some former residents had argued that the legal costs — close to $16 million for the three cases that would be payable from the settlements — were too high.
The lawyers involved argue they spent years taking on the difficult case on the expectation they would be paid only if they won.
Other critics said the compensation was too low for the harm they had suffered, and that the claims process would be too difficult.
But Conway concluded the deals are the best under the circumstances, given the potential for lengthy litigation with uncertain result if she rejected the agreements.
"It's not for the court to impose different settlement terms on the parties," the justice said.
Vici Clarke, whose brother was at Rideau during the early 1970s, said outside court she was pleased and relieved with the settlement.
"No amount of money can compensate for a lifetime of harm," Clarke said.
"To have this part of Canadian history that many people don't know about, to have families' and individuals' experiences listened to and validated, is worth its weight in gold."
Baert called the agreement "a very good settlement."
Attorney General John Gerretsen said he was pleased at the agreement with the former residents who were "harmed."
"We cannot change the past, but we will continue to do everything we can to ensure that all Ontarians — regardless of their abilities — are treated with the compassion, dignity and respect they deserve," Gerretsen said in a statement.
Conway said she would hear arguments over legal fees and costs on Tuesday.