Canada's Old Age Pension (OAP) and the Guaranteed Income Supplement (GIS) are payable to those 65 and older. To be eligible for GIS you must reside in Canada and have a low enough income to qualify. Non-residents of Canada are not entitled to GIS and are subject to a 15% non-resident withholding tax on their OAP, although you can apply for relief on this.

Canadians can qualify for Canada Pension Plan (CPP) commencing at age 60. There are no residency requirements and like OAP it is subject to 15% non-resident w/h tax. If you start receiving your CPP prior to age 65 it will be at a reduced rate compared to what you would get at 65 or older.

I believe you can apply for OAP up to one year before you reach 65 and the CPP up to one year before you are eligible to receive it.