Cattai Estate, Heritage estate in New South Wales, Australia.

Cattai Estate is a former farm and cultural landscape at Cattai, on Wisemans Ferry Road where Cattai Creek meets the Hawkesbury River. Its buildings were constructed between 1804 and 1821, among them the Caddie homestead begun by Thomas Arndell in 1820. The property is now part of Cattai National Park and is owned by the Office of Environment and Heritage.

Thomas Arndell, a First Fleet surgeon, received 240 hectares at the junction of Cattai Creek and the Hawkesbury River in 1804. He began building Caddie homestead around 1820, and by 1810 over seventy percent of arable land in the Cattai area was under cultivation, earning it the name "the granary of the colony." A rust blight in 1863 destroyed the entire crop and ended grain growing here.

The Darug occupied this land for at least 13,000 years, and possibly 45,000, before European settlement. In 1793 Governors Phillip and Hunter noted that the banks of the Hawkesbury appeared ploughed by Darug yam harvesting. The park today holds only a fragment of that homeland, which reached from Broken Bay to beyond the Hawkesbury River.

The estate lies at the junction of Cattai Creek and the Hawkesbury River, reached via Wisemans Ferry Road at Cattai. Governor Phillip had warned of flooding and isolation here in 1794, and the Hawkesbury broke its banks in 1806, so low-lying ground near the creek can be wet. The homestead, begun by Thomas Arndell in 1820, stands within what is now Cattai National Park.

Construction of the mill and granary at Hope Farm began in 1804, and it is considered Australia's first industrial building. No evidence shows the mill ever ran commercially to supply flour to the colony, and by the early 1860s it stood abandoned and in disrepair.