Episode I : A New Hope

Cast (in credits order) verified as complete :

Mark Hamill....                Luke Skywalker
Harrison Ford....            Han Solo
Carrie Fisher....              Princess Leia Organa
Peter Cushing....            Grand Moff Tarkin
Alec Guinness....            Ben (Obi-Wan) Kenobi
Anthony Daniels....         C-3PO
Kenny Baker (I)....         R2-D2
Peter Mayhew (II)....     Chewbacca
David Prowse....              Lord Darth Vader
Phil Brown (I)....              Uncle Owen Lars
Shelagh Fraser....            Aunt Beru Lars
Jack Purvis....                  Chief Jawa/Praying Mantis (Kitik Keed'kak)/Power Droid (EG-6)
Alex McCrindle....          General Dodonna
Eddie Byrne....                Commander Willard
Drewe Henley....            Red Leader
Denis Lawson....            Wedge Antilles (Red 2)
Garrick Hagon....           Biggs Darklighter (Red 3)
William Hootkins....        Jek Porkins (Red 6)
Angus MacInnes....        Dutch (Gold Leader)
Jeremy Sinden....            Tiree
Graham Ashley....          Tiree (Gold 2)
Don Henderson (II)....   General Tagge
Richard Le Parmentier....Admiral Motti
Leslie Schofield....          Imperial Commander #1

(rest of cast listed alphabetically)
Jon Berg....                  Cantina Musician (uncredited)
Doug Beswick....         Cantina Musician (Lirin Car'n) (uncredited)
Janice Burchette....         Martian #2 (uncredited)
Ted Burnett....              Wuher (Mos Eisley Barman) (uncredited)
Stephen Calcutt....         Fly Alien (Tzizvvt) (uncredited)
Gilda Cohen....              Little Aunt Beru (uncredited)
Barry Copping....         Grasshopper (uncredited)
Jenny Cresswell....         Local Girl in Cantina (uncredited)
Alfie Curtis....              Grubby Human (Dr. Evazan) (uncredited)
Maria De Aragon....     Martian #1 (Greedo) (uncredited)
Robert A. Denham....     Crocker #1 (Hrchek Kal Fas) (uncredited)
Peter Diamond....         Imperial Stormtrooper (uncredited)
Sadie Eddon....         Rodent (aka Snitch/Garindan) (uncredited)
Kim Falkinburg....     Djas Puhr (uncredited)
Salo Gardner....         Local Ugly Man #5 (uncredited)
Barry Gnome....         Bat Alien (Kabe) (uncredited)
Isaac Grand....         Bureaucrat #2 (uncredited) Christine Hewitt....Space Girl #1 (Brea Tonnika) (uncredited)
Tommy Ilsley....        Colonel #1 (Ponda Baba) (uncredited)
Joe Johnston....         Death Star Trooper (uncredited)
Annette Jones....         Walrus #2 (uncredited)
James Earl Jones....     Darth Vader (voice) (uncredited)
Joe Kaye....                  Colonel #2 (uncredited)
Jack Klaff....                  Man in Briefing Room (uncredited)
Melissa Kurtz....         Jawa (uncredited)
Tiffany L. Kurtz....        Jawa (uncredited) Anthony Lang.... Local Ugly Man #3 (uncredited)
Laine Liska....              Four Eyes (Muftak)/Cantina Musician (uncredited)
Mahjoub....                  Jawa (uncredited)
Alf Mangan....              Snaggletooth #2 (Takeel) (uncredited)
Rick McCallum....     Imperial Stormtrooper (Special Edition) (uncredited)
Grant McCune....         Death Star Gunner (uncredited)
Jeff Moon....                  Local Ugly Man #6 (uncredited)
Mandy Morton....     Local Girl #2 (Swilla Corey) (uncredited)
Lorne Peterson....     Massassi Base Rebel Scout (uncredited)
Marcus Powell....     Flash Gordon Midget (Rycar Ryjerd) (uncredited)
Shane Rimmer.... '    Red 5' Technician (uncredited)
Pam Rose....             Weird Girl (Leesub Sirln) (uncredited)
Arthur Rowton....     Snaggletooth #1 (Zutton) (uncredited)
Erica Simmons....     Walrus #1 (Mosep) (uncredited)
Tom St. Amand....     Cantina Musician (uncredited)
Angela Staines....     Space Girl #2 (Senni Tonnika) (uncredited)
Koo Stark....              Camie (scenes deleted) (uncredited)
George Stock....     Bureaucrat #1 (uncredited)
Roy Straite....         Local Ugly Man #2 (uncredited)
Peter Sturgeon....     Crocker #2 (Sai'torr Kal Fas) (uncredited)
Peter Sumner....     Death Star Officer (uncredited)
John Sylla....         Stormtrooper (voice) (uncredited)
Tom Sylla....              Stormtrooper (voice) (uncredited)
Malcolm Tierney.... Officer in Detention Area (uncredited)
Phil Tippett....         Cyclops (Myo) (uncredited)
Larry Ward....         Martian #1 (Greedo) (voice) (uncredited)
Diana Sadley Way.... Martian #1 (Greedo) (uncredited)
Fred Wood....         Local Ugly Man #1 (uncredited)

Courtesy IMDB