Lingmerth, Francesco Molinari, Matt Jones, Tim Clark, Harris English and Daniel Berger have been added to the field for the year's third major after it was determined that not all the remaining berths in the 165-man field would be taken up by qualifiers.
It will be Lingmerth's first appearance at the tournament, and comes following his victory at Muirfield Village last month.
Molinari, who finished in a tie for ninth at The Open in 2013, was outside of the top 50 in the world rankings when the cut off was made, but has since climbed to 43rd.
Jones finished in a tie for 54th in his Open debut last year, while Clark will be making his 10th appearance. The 25-year-old English boasts a top 20 finish in 2013 as his best effort in three attempts. PGA rookie Berger will be making his tournament debut.