Jane Austen's House Museum in Hampshire, southern England, where the 19th century author penned her six novels, said Clarkson had accepted its offer of £157,740 ($253,300, 187,500 euros) for the ring.
The museum had been outbid by Clarkson at the original auction, but launched a campaign in August to raise buy-back funds from Austen fans around the world.
Curator Mary Guyatt said the museum was "thrilled" to be bringing the gold and turquoise ring "home".
"The museum has been stunned by the generosity and light-footedness of all those who have supported our campaign," she said.
"Visitors come from all around the world to see the house where she once lived and we will now take great pleasure in displaying this pretty ring for their appreciation."
The ring, one of only three surviving pieces of jewellery known to have belonged to the celebrated novelist, is due to go on display at the museum early next year.
Known for their gentle mocking of the landed gentry, Austen's novels including "Pride and Prejudice" and "Emma" are among Britain's best-loved classics.
Austen fan Clarkson, whose hits include "A Moment Like This" and "Since U Been Gone", has sold more than 20 million albums.
She shot to fame as the winner of the "American Idol" TV talent contest in 2002.
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The museum had been outbid by Clarkson at the original auction, but launched a campaign in August to raise buy-back funds from Austen fans around the world.
Curator Mary Guyatt said the museum was "thrilled" to be bringing the gold and turquoise ring "home".
"The museum has been stunned by the generosity and light-footedness of all those who have supported our campaign," she said.
"Visitors come from all around the world to see the house where she once lived and we will now take great pleasure in displaying this pretty ring for their appreciation."
The ring, one of only three surviving pieces of jewellery known to have belonged to the celebrated novelist, is due to go on display at the museum early next year.
Known for their gentle mocking of the landed gentry, Austen's novels including "Pride and Prejudice" and "Emma" are among Britain's best-loved classics.
Austen fan Clarkson, whose hits include "A Moment Like This" and "Since U Been Gone", has sold more than 20 million albums.
She shot to fame as the winner of the "American Idol" TV talent contest in 2002.
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