Dumbledore's Army

Dumbledore's Army (often referred to as the D.A.) is an association in the Harry Potter series by J.K. Rowling. It is started in Harry Potter and the Order of the Phoenix and continued in the last book, Harry Potter and the Deathly Hallows by members Neville Longbottom, Ginny Weasley, and Luna Lovegood. This is an association created to prepare some pupils for beating Voldemort.

The leader, Harry Potter, teaches his friends how defend themselves against the Dark Lord. The idea for the D.A. came from Hermione Granger, who wanted the students to learn defensive spells which were not being taught by the new Defense Against the Dark Arts teacher, Dolores Umbridge. 

Founders: Harry Potter, Ron Weasley, and Hermione Granger 

Members:
Hannah Abbott,
Katie Bell,
Susan Bones,
Terry Boot,
Lavender Brown,
Cho Chang,
Michael Corner,
Colin Creevey, Dennis Creevey,
Marietta Edgecombe,
Justin Finch-Fletchley,
Seamus Finnigan,
Anthony Goldstein,
Angelina Johnson,
Lee Jordan,
Neville Longbottom,
Luna Lovegood,
Ernie Macmillan,
Padma Patil,
Parvati Patil,
Zacharias Smith,
Alicia Spinnet,
Dean Thomas,
Fred Weasley, George Weasley,
Ginny Weasley

Nigel Wolpert was only in the movie’s D.A. He is a character that is Colin and Denis combined, so he was never actually in the books. (This means his name was not in the original D.A. List.)

In Harry Potter and the Deathly Hallows when Harry, Ron and Hermione were not in Hogwarts, Neville Longbottom became the leader.