GO Transit is the inter-regional transportation authority of the Golden Horseshoe, which includes the Greater Toronto and Hamilton Area.  It is Canada's oldest regional transit system, first serving passengers in 1967.
 The service area of GO Transit is divided into a number of fare zones, each of which belonging to a number of fare corridors.  Fares on GO Transit are based on the distance between originating and destination fare zones.  Tickets between two fare zones are valid for travel between the two fare zones stated on the ticket, as well as between any two fare zones that lie between them on the same fare corridor.  Tickets are not generally issued between two fare zones on different corridors, with the following notable exceptions:
 As all GO Transit tickets are only valid for continuous trips of no more than two and a half hours, multiple tickets may be needed for longer trips.
 Fare zones 1–9, 19, 59, 70, 77, 79, 89 and 90 (shaded in green) are located within Toronto.
 GO Transit offers three passenger fare classes: adult, senior and student.  Senior fares are available for passengers over the age of 65. As of March 9, 2019, passengers under the age of 12 can ride free on all GO Transit trains and buses.
 Student fares are only available for those with acceptable student identification:
 Up until July 31, 2012, GO Transit offered five types of fares:
 GO Transit stopped selling two-ride and ten-ride tickets on June 1, 2012 and stopped accepting two-ride and ten-ride tickets on July 31, 2012, in favour of using Presto Cards exclusively; paper monthly passes have been discontinued since 1 January 2013; day passes remain available for purchase.  Passengers may convert any unused rides on their tickets to equivalent value on a Presto Card before the end of 2012.
 There is no distinction between bus and train service.
 Fares between two fare zones for a particular type of ticket and passenger category are based on multiples of the standard (adult single-ride) fare as follows:
 Fares are rounded to the nearest $0.05 for single-ride fares and day passes and $1.00 for monthly passes, after fare multiples are applied.  The minimum adult single-ride fare (for travel on GO Transit within one fare zone) is always $4.50; other fares depend on the fare zones travelled.
 Presto cards and contactless credit cards are accepted on GO Transit.  Passengers must tap their cards against the reader upon embarking and disembarking the train or bus.  Upon embarking, the minimum fare ($5.30) is always deducted from Presto cards, with fare adjustments performed as the passenger disembarks. With credit cards, charges are processed at the end of the day as a single charge combining all the day's trips.
 The following credit cards are accepted: VISA, MasterCard and American Express.
 Failure to tap the card upon disembarking ("missed tap-off") will cause the maximum fare to be deducted, under the assumption that the passenger travelled to the point furthest away from the origin point. (For example, passengers failing to tap off when boarding at Union Station will be assessed the fare travelling from Union Station to Kitchener GO Station, the point furthest away on any GO train route serving Union Station.) Passengers regularly travel by GO train may also set a "default trip" between two GO train stations, allowing them to avoid tapping their cards upon disembarking; passengers doing so will have the appropriate fare deducted upon embarking at either endpoint. The default trip is not available on contactless credit cards.
 Adult and student passengers using the Presto card receive a further fare discount, depending on the number of trips that have been made per month between two fare zones.
 If there are rides between different sets of fare zones, the discounts after the 30th trip (students) and 35th trip (adults) will be based on the total value of rides taken so far; the fare discounts are structured so that adult and student passengers pay less over the course of a month compared to paying for a paper monthly pass ahead of time; the discrepancy is to encourage passengers to adopt the Presto card over the paper monthly pass.
 GO Transit offers fare integration services with local transit providers, as well as with Via Rail.
 Via Rail offers interline tickets with GO Transit, where passengers may travel on GO Transit trains and connect with Via Rail trains at any GO station also offering Via Rail services (Aldershot GO Station, Brampton GO Station, Georgetown GO Station, Guelph Central GO Station, Guildwood GO Station, Kitchener GO Station, Niagara Falls railway station (Ontario), Oakville GO Station, Oshawa GO Station, St. Catharines railway station, and Union Station) or vice versa on one ticket; the Via Rail ticket acts as a GO transit proof of payment on the GO transit leg.  Via Rail interline tickets are not valid for GO buses when trains are not running.
 Via Rail also offered the GO-Via Pak, which allowed holders of GO Transit monthly passes or 10-ride tickets (between applicable fare zones) to ride between Union Station and five GO Stations (Aldershot, Brampton, Georgetown, Oakville, Oshawa) on Via Rail trains which stopped at those stations.  The GO-Via Pak was priced at the difference between 10 adult single fares and the equivalent 10 adult economy fares on Via Rail.  The GO-Via Pak could not be used with the Presto Card.  The GO-VIA Pak was no longer sold after December 15, 2012 and was not accepted as of January 1, 2013.
 Fare integration services may exist between GO Transit and local transit providers, where customers may ride GO buses within local service areas using appropriate local proof-of-payment (tickets and/or passes) at no additional cost; GO Transit will also issue a transfer for further travel on local transit providers upon request.  Passengers paying by cash or travelling outside the local service area must pay GO transit fares.  Passengers using Presto Card will be assessed GO transit fares, although plans are in place for local fares to be assessed instead of GO transit fares whenever they are lower.
 As of March 14, 2022 most local transit systems - except Toronto Transit Commission and UP Express - that connect with GO Transit offer free admission so long as the customer swipes their Presto card on the connecting vehicle.  In some cases (where applicable), passengers may also present their GO Transit proof-of-payment (a day pass or single-ride ticket) to the local transit operator.
 Passengers using the Presto card or contactless credit card (where accepted) will automatically be assessed the co-fare where appropriate, depending on the status of the local transit operator's integration with the Presto Card or contactless credit card.  If the local transit operator does not currently accept the Presto Card or contactless credit card, the co-fare is not applicable with these payment methods.
 Although separate fares apply when transferring between TTC and GO Transit.  However, the TTC offers a program called "TTC Times Two", for TTC customers who pay their TTC fares by tokens or cash and obtain a paper transfer may board a second TTC service vehicle using that TTC paper transfer from the first TTC leg if there is a GO Transit trip in between at designated transfer points only (the restrictions do not apply for customers paying by Presto). Note that GO Transit proof of payment is not needed for this program. In addition, passengers connecting to TTC Route 38 (serving University of Toronto's Scarborough campus) from Rouge Hill GO Station may travel for free with GO Transit proof of payment.