Representatives from Meta, TikTok and Google are appearning before the Oireachtas Committee on Media.
The hearing is discussing online safety, disinformation and media literacy.
X, formerly known as Twitter, declined an invitation to attend the hearing citing ongoing legal proceedings.
The company said it is willing to respond to the committee's questions in writing and to meet with them privately.
Last month's riots in Dublin have placed renewed focus on the role of social media companies when it comes to the removal of harmful content and disinformation.
Meta, the parent company of Facebook and Instagram, told the committee that in Ireland it removed almost 1,000 pieces of misinformation in the first half of this year from Facebook because the content violated its community standards.
It also applied warning labels to 1.1 million pieces of content on Facebook originating from Ireland that were rated as false by fact-checkers.
In his opening statement to the committee, Dualta Ó Broin, Head of Public Policy for Meta in Ireland, said the company has written clear polices on online safety, has developed sophisticated technology to detect and prevent abuse from happening, and has provided tools and resources for users to control their experience or get help.
"We regularly consult with experts, advocates and communities around the world to write our rules and we constantly re-evaluate where we need to strengthen them," said Mr Ó Broin said.
"Our content enforcement relies on a combination of people reporting content, AI technology and human reviews," he added.
TikTok told the committee it is continuing to grow its operations in Ireland with over 3,000 employees in diverse roles, including data privacy and TikTok's trust and safety team.
"Our Community Guidelines reflect our values and establish the kind of behaviour we expect on our platform," Susan Moss, Head of Public Policy at TikTok in Ireland said in her opening statement.
"TikTok proactively seeks out and removes content which violates these guidelines," Ms Moss said.
"We place considerable emphasis on proactive content moderation and the vast majority of violative content is identified and removed proactively before it ever receives a single view or is reported to us," she added.
Speaking ahead of the meeting, Committee Cathaoirleach Niamh Smyth said the hearing will allow members to engage in detail with some of the major social media providers.
"Our engagement with these companies will allow them to demonstrate how they are actively leading in the eradication of the very prevalent false information and clickbait style content among users of their platforms," Ms Smyth said.
In a separate session, the Media Committee will hear from the Finnish Audiovisual Institute (KAVI) which provides and promotes media education and media literacy in Finland.
Sinn FéiN TD Imelda Munster expressed her disappointment that X/Twitter had declined an invitation to attend the hearing.
"They say said they would be willing to correspond with us in private session but I don't think it is good enough that they are refusing to attend a public session," Ms Munster said.
Fianna Fail TD Christopher O'Sullivan also expressed his disappointment.
"I think it is an absolute disgrace that Twitter/X haven't agreed to participate in this meeting today because all social media giants have a role to play in terms of curbing the spread of disinformation," Mr O'Sullivan said.
"The scale of disinformation on social media outlets is out of control," he added.
Fine Gael TD Ciaran Cannon said the owner of X, Elon Musk, should "desist from commenting on affairs in Ireland which he clearly knows nothing about" and added that he should be "ashamed" of some of his recent posts.
The representatives from Meta and TikTok said policing their platforms is an ongoing process.
"It is a constant challenge, we are not going to claim we have this sorted and that we are going to stop investing in this, we have to continue to evolve our operations," Meta's Dualta Ó Broin said.
TikTok's Susan Moss said there is "room for improvement".
"I absolutely recognise that. We don't create a permissive environment for this type of behaviour to find a way to grow," Ms Moss said.
Asked about claims that it was suppressing pro-Palestinian content on its platforms, Meta said it strives to apply its community standards fairly and that when it comes to conflicts, it will frequently get complaints from both sides.
