Tuesday's 1-0 loss away to Austria meant the Republic of Ireland no longer has any realistic hope of qualifying for next year's World Cup. It proved to be the last straw for the Football Association of Ireland, which had heralded Trapattoni as the most successful club coach in history when hiring him in 2008.
The federation and Trapattoni said in a joint statement they mutually decided to end a contract that was supposed to run through June. The FAI also cut ties with Trapattoni's longtime assistants, Marco Tardelli and Franco Rossi.
"We leave this country with emotion because we understand the Irish supporters, who have a well-deserved international reputation and they have our utmost respect," Trapattoni, 74, said in his statement. He cancelled a planned news conference.
Trapattoni's qualification campaign for the 2014 World Cup in Brazil featured an Ireland team with little attacking flair, a weak midfield and an unusually shaky defence. The opening home match, a 6-1 drubbing by Group C favourite Germany last October, was Ireland's worst home defeat since 1931.
The FAI offered no hint when it would hire a long-term successor. Ireland still has two World Cup qualifiers next month in Germany and at home versus Kazakhstan, but analysts agreed that Ireland probably would install a temporary caretaker.
Irish betting company Paddy Power listed former Celtic, Aston Villa and Sunderland manager Martin O'Neill as the clear favourite to succeed Trapattoni. O'Neill, from Northern Ireland, is without a coaching job and has worked with many of Ireland's players at English and Scottish club level.
Steve Staunton, Trapattoni's predecessor as Ireland manager, said it had been a mistake to hire a coach so foreign to Irish players and culture. Trapattoni, lacking fluency in English, struggled to communicate with his team, didn't watch the club performances of Irish players in person, and spent most of his time in his native Milan.
Staunton said he wanted the next manager to be from Ireland or Britain, "someone who knows what the Irish boys are about and knows the mentality."
Criticism of the often inflexible, long-ball tactics deployed by Trapattoni had swelled since 2012, when Ireland lost all three of its European Championship group matches in one-sided fashion. He also was lambasted for eccentric squad selections that failed to promote young talent in favour of lacklustre veterans who stuck from his initial 2008 squads.
Trapattoni often countered by noting — too frankly for some Irish ears — that Ireland's top players were mostly run-of-the-mill talents who struggled for regular playing time in their British clubs.
Brian Kerr, a Dubliner who coached Ireland in 2003-05, said Trapattoni's negative defensive tactics downplayed his players' skills and hurt their morale.
"I don't agree with him when he says Irish players are not capable of passing the ball around. They are professional footballers, many playing in the Premier League. They can pass the ball. I've seen them do it," Kerr said.
Dubliners seeking a return to Ireland's 1990s glory days under Jack Charlton had celebrated the 2008 hiring of Trapattoni, waving Irish flags adorned with the Italian's grandfatherly face above the slogan "In Trap we trust."
Ireland had not qualified for an international tournament since 2002. But Trapattoni guided his squad to the verge of qualification for the 2010 World Cup in South Africa — only to be denied by an egregious, and uncalled, handball by Thierry Henry that produced a decisive extra-time goal for France in its playoff with Ireland. The FAI appealed in vain to FIFA for a slot in South Africa.
Trapattoni received stronger praise for leading Ireland in 2012 into the European Championship, its first time in that tournament since 1988.
But speculation on his dismissal steadily grew after Ireland lost all three group matches in Poland, where the Irish were paired with eventual finalists Spain and Italy. They respectively trounced the Irish 4-0 and 2-0.
Ireland's last positive result of note under Trapattoni was a 1-1 friendly draw against England at Wembley Stadium in May.
Trapattoni came to Ireland with a stunning record of success at club level. He won six Italian titles with Juventus and one with Inter Milan, the Bundesliga with Bayern Munich, the Portuguese league with Benfica and the Austrian league with Salzburg.
He also won three UEFA Cups, the Cup Winners' Cup, the European Super Cup and the European Cup.
But his four years in charge of Italy were disappointing. They featured a second-round 2002 World Cup defeat by South Korea and failure to advance from the group stages of Euro 2004.