Under the new boundaries, the area extends from the mouth of the Clutha River in the north, to the Mataura River at Fortrose in the south, and extends inland to encompass Waiarikiki.
The area was originally defined from the Nuggets in the north, to Slope Point in the south.
Ron Tyrell, a historian with the Catlins Historical Society, submitted an application to the New Zealand Geographic Board in July 2008 to have the name "The Catlins" officially recognised as a place name.
This was accepted, and published in the New ZealandGazette in May last year.
However, the Catlins Historical Society lodged an objection to the proposed boundaries, on the grounds that the area operated as a tourism entity between the two rivers.
Heather Buckingham, chairwoman of Tourism Catlins, said since Tourism Catlins had been operating, it had defined its boundaries as between the two rivers.
"We are all very passionate about The Catlins, and thrilled the board has seen fit to accept the area we have defined."
Mrs Buckingham said the area inland included several forest blocks that make up The Catlins Forest Park.
"It's an area that's sort of bush and sea and wildlife."
With the area clearly defined, Mrs Buckingham said tourism could be managed in a more sustainable way.
