TROA was established in late 1977 when the organisers of five Irish International rallies and the Manx International Rally came together to form a unified championship series. The inaugural ITRC season ran in 1978 over six events: the Galway International Rally, Circuit of Ireland Rally, Donegal International Rally, Ulster Rally, Cork 20 International Rally, and the Manx International Rally.
The championship expanded to seven rounds in 1984 when the Rally of the Lakes attained International status and both it and the Galway International Rally featured on the calendar simultaneously. A further broadening came in 2002 when the Jim Clark Rally in Scotland became the first non-Irish event to join the series, though it was dropped again in 2010 alongside the Manx International Rally due to declining ITRC competitor entries at both events.
The West Cork Rally joined as a full championship round in 2015, restoring the seven-event format that remains the standard structure.
The seven rounds of the modern ITRC are:
Galway International Rally
West Cork Rally
Easter Stages Rally
Killarney Rally of the Lakes
Donegal International Rally
Ulster Rally
Cork 20 International Rally
Since 2016, World Rally Cars have not been eligible to score championship points, though they may still win events outright. The championship is scored on a driver's best six results from seven rounds, with the winner of each round receiving 21 points. Finishers outside the top 10 still receive 1.5 points, and each crew that enters and starts an event earns one bonus point for participation.
Three additional championships run concurrently with the main ITRC under their own regulations: the ITRC Junior Championship, the ITRC Historic Championship, and the ITRC Modified Tarmac Championship. This structure allows competitors of varying experience levels and car eras to contest for titles within the same event weekends.
The 2020 season was cut short after its opening round at Galway when the COVID-19 pandemic forced the suspension of all motorsport, and TROA ultimately cancelled the championship in April 2020. The 2021 season was cancelled entirely in February of that year as pandemic restrictions continued across both jurisdictions.
A full calendar returned in 2022, and the following seasons saw competitive battles at the front of the field. The 2019 championship was won by Craig Breen, co-driven by Paul Nagle, after taking five of the season's round victories. The 2025 title went to Callum Devine for his second championship in three seasons, having won all four rounds he entered despite the opening Galway round being cancelled due to infrastructure damage caused by Storm Éowyn.
The ITRC holds a distinctive place in European rallying as a high-level domestic series run entirely on closed public roads rather than the mixed or gravel surfaces common to most national rally championships. Its events, including the long-standing Donegal International Rally and Ulster Rally, have a rich history dating back to the formative years of Irish motorsport, and the series has been a launching pad for drivers who later competed at World Rally Championship level.