Wild Nephin National Park in Mayo has been twinned with Yosemite National Park in California in a five-year sister park agreement.
The Department of Heritage said the agreement will see the National Parks and Wildlife Service share knowledge across the Atlantic and in turn learn from a sister park to help conservation and improve biodiversity in Wild Nephin.
The parks will also collaborate in areas including visitor, forestry and wilderness management.
Speaking on RTÉ's Morning Ireland, Superintendent of Yosemite National Park Cicely Muldoon said it was a "great day" for both parks.
"As we join in sister parks we will begin to share our research, our information, our picnics, in managing national parks, which really share the same issues all over the world," she said.
"And today, we will join one of the wildest places in Ireland with one of the wildest places in the United States."
Parks all share the "great threat of climate change which knows no boundaries", she said.
"We are all working hard wherever we are on the planet to protect native species, to improve habitat, to build some resiliency into the landscapes, so these places can survive for our children and our grandchildren," Ms Muldoon said.
Yosemite National Park has one of the biggest wildfire programmes in the US national park system and can share that knowledge with Nephin, she added.
"We hope to work closely with Nephin on that threat and on other forest management principles," Ms Muldoon said.
Located in northwest Mayo, Wild Nephin National Park was designated as Ireland's sixth National Park in 1998.
The park is home to Owenduff Bog, one of the largest intact active blanket bog systems in Western Europe, along with a wide range of protected species and habitats, including internationally important freshwater river systems and associated habitats.
Yosemite National Park covers more than 300,000 hectares, 95% of which is designated wilderness.
It was designated a National Park in 1890 and is home to five of the world’s highest waterfalls, granite domes and wells, deep valleys, giant sequoia groves and lakes.
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