Gordon Elliott has had his training licence suspended for 12 months, with the last six suspended.
The decision was taken following a hearing by the referrals committee of the Irish Horseracing Regulatory Board (IHRB) on Friday.
It was convened in the wake of the controversial photo of the trainer sitting on a dead horse, which was circulated on social media.
The IHRB was also awarded costs of €15,000.
In a statement, the board said the sanctions will take effect from March 9th.
It said the referrals committee found Mr Elliott in breach of Rules 272(i) - in that he acted in a manner which was prejudicial to the integrity, proper conduct and good reputation.
In the decision, Mr Justice Groarke said: "A photograph was published on social media this past weekend showing licensed trainer Gordon Elliott sitting astride a horse who appeared to be dead.
"This photograph caused considerable public dismay and anger given not only what was depicted but also the jovial demeanour and gesticulations of Mr Elliott.
"In short order, the IHRB received an avalanche of complaints and the matter was rightly and fully scrutinised on the media."
The committte said it shares "the public disquiet and believes and insists that animals, either alive or dead, must receive proper respect most especially from those in whose charge they happen to be."
"The consequences of Mr Elliott’s actions have damaged the reputation of the Irish racing and the thoroughbred industry", it said.
But it added that Mr Elliott expressed what it believes to be a genuine remorse.
"We believe that he genuinely accepts that he was extraordinarily foolish to participate in the way he did," it added.
The statement also said Mr Elliott "fully cooperated" with the investigation, "put his hands up at the earliest opportunity and fully accepted that his actions had offended many people".
Mr Elliott has not contested the the photograph, and said it was taken in 2019 following the death of a horse.
'One of the harshest punishments'
Racing journalist Kevin Blake told The Hard Shoulder the IHRB came down heavy.
"As someone that follows IHRB disciplinary matters very closely, this would rank as one of the harshest punishments in the recent history of Irish racing.
"It's very hard to find a comparable case to this - but maybe the most comparable one, about three or four years ago Davy Russell lost his cool with a horse at the start of a race and punched it.
"And he received on the day a caution, the leniency of that was later appealed and he got a four day suspension.
"So obviously 12 months with six months suspended is a massive difference."
Blake said generally speaking, the IHRB airs on the side of leniency.
"But in my experience of these types of their disciplinary matters, I don't think you could say they're sherped this.
"For a trainer in Gordon Elliot's position, the financial and professional ramifications for this will be very, very heavy".
'Paying a very heavy price'
In a statement following the ruling, Mr Elliot said: "I accept my situation and my sanction and am satisfied with my engagement with the Irish Horseracing Regulatory Board. It is not an easy job to sit on the panel but I was dealt with fairly.
"I am in this situation by my own action and I am not going to dodge away from this.
"With my position in the sport I have great privileges and great responsibility.
"I did not live up to that responsibility. I am no longer the teenage boy who first rode a horse at Tony Martin’s 30 years ago.
"I am an adult with obligations and a position in a sport I have loved since I first saw horses race.
"I am paying a very heavy price for my error but I have no complaints.
"It breaks my heart to see the hurt I have caused to my colleagues, family, friends and supporters. I have a long road ahead of me but I will serve my time and then build back better.
"Horses are my life. I love them. No one comes into racing for money - it is a hard way to make a living.
"We are here because we love the horses. Anyone who has visited my stables at Cullentra will see the meticulous care with which we treat our horses.
"I was disrespectful to a dead horse, an animal that had been a loyal servant to me and was loved by my staff.
"I will carry the burden of my transgressions for the rest of my career.
"I will never again disrespect a horse living or dead and I will not tolerate it in others," he added.
Speaking earlier this week, Minister of State for Sport Jack Chambers said he would not be comfortable seeing Mr Elliott taking part in Cheltenham.
"I was absolutely shocked, appalled and horrified by that photo and by his actions," he said.
"I think he needs to held fully accountable. I think anyone who saw it was shocked by it and we need to uphold the highest welfare standards in Ireland.
"Any and every sanction should be on the table. It is important, we have a significant amount of equestrian activity in Ireland and we need to set a really high bar when it comes to welfare standards."