Kevin Seaward has set a new Northern Ireland record of 2:10.10 after finishing 24th at the Seville Marathon.
It is well inside the Olympic qualifying standard for Tokyo and eclipses Paul Pollock's previous NI record of 2:10.25.
Seaward, 36, joins Pollock in achieving an Olympic qualifying time, however only three spots are available in the Ireland team for the Games.
Stephen Scullion has secured his spot in Tokyo at January's Houston Marathon.
Scullion's run to fifth place was 22 seconds outside the qualifying standard but the Houston event was a gold label race which secured his Olympic place.
If another athlete records the qualifying time before the qualification period ends on 31 May then Athletics Ireland will have a selection process for the Games.
Seaward's time in Spain was the second fastest time by an Irish athlete behind 1984 Olympic silver medallist John Treacy, who holds the Irish record of 2:09.15 in Boston in 1988.
The Belfast man's time cut three minutes and 29 seconds off his previous personal best set in Berlin last September.
That time was the fastest marathon time by an Irishman since 2002 but four men have since gone quicker than that amid a remarkable rise in standards.
Mayo man Hugh Armstrong also produced a big personal best on Sunday in Seville as he clocked 2:12.16 - one minute and 56 seconds inside his previous mark - and 46 seconds outside the Tokyo standard.
Armstrong may consider having another go before the May deadline with the London Marathon among his possible options.
Loughborough-based Seaward finished fourth in the 2018 Commonwealth Games marathon in Australia and was an Olympian in Rio in 2016.
Seaward and Pollock both have the same coach in Andy Hobdell.