Dana Erlich was speaking after a screening of footage for reporters at the Israeli embassy which showed Hamas' October 7 attack.
She said the footage, which included an attack on a kibbutz and Re'im music festival one month ago, was "historically important".
Ms Erlich said: "It is the most horrific attack on Jewish people since the Holocaust."
She said the footage in the 43-minute video was collected from the cameras of victims, emergency personnel, and dead Hamas operatives.
It included clips of Hamas fighters appearing to kill Israelis at various locations and stills of dead children.
The compilation includes a depiction of a Hamas ambush by shooting occupants of a car at the gate of the Be'eri kibbutz in southern Israel.
It goes on to show fighters shooting the tyre of an ambulance, a dog, and firing into homes.
Reporters also saw footage which appeared to show a father attempting to escort his children to safety at a different settlement, before he is killed after a grenade attack.
CCTV footage then shows the children crying, one of whom says they can no longer see from one eye.
Another video appears to show a Hamas fighter swinging at the neck of a man on the ground with a garden hoe.
At various stages, numerous dead bodies are shown strewn across roadways and in ditches.
Victims have been shot and some bodies have been badly burned.
Other collected clips show several dead people in individual rooms and Hamas fighters firing at the bodies of the deceased.
Still photos of dead babies, some with burned bodies, were also shown to reporters.
At points, Hamas fighters take selfie footage where they are shown to be smiling and cheering near dead Israelis.
The video shown at a board room in the Israeli embassy also offered various views at different stages throughout and after the attack on the Re'im music festival.
Stills appear to show that some of the victims were bound and gagged before being killed.
Hamas fighters armed with assault rifles, RPGs and weapon-mounted pick-up trucks are shown taking several Israelis hostage throughout the footage.
Reporters were told that the footage depicted the killing and dead bodies of 138 people, which the embassy said was less than 10% of the total killed on October 7.
Ms Erlich said she wanted the country's parliamentarians to view the footage at another screening.
Asked about how the Irish-Israel relationship has developed since October 7, the ambassador responded: "This horrible terror attack shows terror knows no borders."
Ms Erlich, who took up the Dublin role less than three months ago, said she was familiar with pro-Palestinian sentiment throughout Ireland and political parties.
However, she said she was "surprised" by the public reaction to October 7 and the ongoing conflict.
She said she did not hear protesters condemn Hamas or call for the release of hostages.
Ms Erlich said Jewish people are becoming more concerned for their safety, adding there was a "wave of antisemitism rising" internationally.
The ambassador said Jewish people in Ireland were afraid to speak up publicly about the conflict, even in a "balanced way".
She said that protesters chanting "from the river to the sea, Palestine will be free" was a call for the elimination of Israel.
Asked if the perception of Ireland being pro-Palestinian meant it could play a role as an interlocutor in resolving the conflict, Ms Erlich said she did not know if Ireland "wants to play that part".
She said nations who take that position are usually not aligned with "any side in particular" and need to be critical of both parties.
She said she understood that Ireland was militarily neutral, but added: "I don't think it is politically neutral."
The ambassador said she had seen more persistent criticism towards Israel from Ireland.
Ms Erlich said that there were still rocket and missile attacks on Israel every day, adding: "It seems like people here forget that."
She said she recognised that Irish government figures had issued "strong condemnations" of Hamas' attack.
"We are fighting this terror together."
Asked if she hoped the footage would change the Irish government's rhetoric on the conflict, Ms Erlich said she wanted to invite politicians to view the footage at a later date and part of the role of the embassy was to strengthen diplomatic relations.
"That is why we are here."
She said the embassy was ready to answer "difficult questions" about the conflict.
She said private screenings of the footage being carried out globally are to "bear witness" and "make sure the world knows" about the extent of the Hamas attack.
She called on Ireland to remember Irish-Israeli citizen Kim Damti, who died after the music festival attack, and eight-year-old Israeli-Irish girl Emily Hand, who is believed to be a hostage of Hamas in Gaza.
Ms Erlich said she had been in contact with Emily's father Tom and her sister Natalie about the family's "tragic" experience.
She said: "We will do anything we can to help speed their release."
Asked about the verification of the footage, she said it mostly came from body-cameras worn by killed or captured Hamas fighters, but also included footage uploaded by Hamas to social media as well as video and stills from Israeli first responders.
Speaking after the screening, Ms Erlich said "the most horrific" thing about the October 7 attack was that many families still do not know if their relatives were killed or taken hostage as there are many unidentified body parts or remains from which DNA cannot be recovered.
The ambassador said she had "many friends" at the musical festival during the attack
She said Israeli authorities believe as many as 1,500 Hamas operatives entered Israel and were planning for fighting for at least one month.
Asked if she believed the graphic video showed justification for Israel's response in Gaza, Ms Erlich said: "This is not an equation."
She said Israel was trying to "get our people back" and "defend our people".
Ms Erlich said a "lot of questions" had been raised about the Israeli intelligence sector's failure to detect the incoming attack and that a "thorough investigation is needed" in the future.
However, she said the current focus is on the ongoing war.
When Ms Erlich was also asked about the targeting of refugee camps, she responded saying Israel was targeting "terrorists" and that international law meant a valid military target includes a location from which you are being fired upon.
She said Israel was not carrying out indiscriminate attacks and was trying to operate with "less civilian casualties".
Asked about the humanitarian situation in Gaza, Ms Erlich said: "We are all concerned for the situation in Gaza."