The Grand Master award is not given out every year; it acknowledges a lifetime of excellent work. While it is not a Nebula, it tends to be handed out as part of the Nebula Award Ceremony.
1975 Robert A. Heinlein
1976 Jack Williamson
1977 Clifford D. Simak
1979 L. Sprague de Camp
1981 Fritz Leiber
1984 Andre Norton
1986 Arthur C. Clarke
1987 Isaac Asimov
1988 Alfred Bester
1989 Ray Bradbury
1991 Lester del Rey
1993 Frederik Pohl
1995 Damon Knight
1996 A. E. Van Vogt
1997 Jack Vance
1998 Poul Anderson
1999 Hal Clement
2000 Brian Aldiss
2001 Philip José Farmer
2003 Ursula K. Le Guin
2004 Robert Silverberg
2005 Anne McCaffrey
2006 Harlan Ellison
2007 James Gunn
2008 Michael Moorcock
2009 Harry Harrison
2010 Joe Haldeman
2012 Connie Willis