| ARDA | Variant | Designer | Players |
| rm64 | Cabinet Diplomacy | Steve Doubleday | 21 |
| rm75 | Cabinet Diplomacy II | Phil Reynolds | 7 |
| ea07 | Canton Diplomacy | Paul Webb | 7 |
| us02 | Capitalist Diplomacy | Dave Tant | 9 – 12 |
| us10 | Capitalist Diplomacy (circa 1897) | Kerry Slavin | 7 |
| us07 | Capitalist-Dippy | Lukas Kautzsch | |
| us08 | Capitalist-Dippy II | Per Westling | |
| lc02 | Caribbean Diplomacy | Steph Mabie | 5 |
| lc06 | Caribbean Diplomacy II | Steph Mabie | 4 |
| rs26 | Cartel Diplomacy | Brown and Loveys | 7 |
| uu11 | Carthage | Hartley Patterson | |
| uu03 | Cat Diplomacy | Ernie Melchior | 3 |
| rb30 | Catastrophe Diplomacy | ?? | 7 |
| rz03 | Catspaw Diplomacy | Ron Melton, Mike Ritter and Kevin Rowland | 3 |
| pr03 | Caucasia | Christian Dreyer | 5 |
| hb08 | Centenary | William Preston | 7 |
| lc01 | Central American Diplomacy | Russell Fox | 7 |
| rb50 | Chained Lightning | Steve Doubleday | 7 |
| rh13 | Chaos (Judge Version) | Author Unknown | 34 |
| rs48 | Chaos Diplomacy | Richard Weiss | 7 |
| rs05 | Chaos I | D. Miller | 7 |
| rh06 | Chaos II | Michel Feron | 34 |
| rg06 | Character Diplomacy | Fred Davis | 7 |
| rg15 | Character Diplomacy (Batyville Version) | Ralph Baty | 7 |
| rg14 | Character Diplomacy II | John Galt and Fred Davis | 7 |
| ec01 | Chinese Diplomacy | Tom McCloud | 6 |
| ug16 | Chromatic Diplomacy | James Millington, Robert Schone and Lynsey Smith | 5 |
| fc01 | Chronicle | Les Walker | 7 |
| rb121 | Chronos | Wes Malkin | 7 |
| vb02 | Circle Variant | Mark Weidmark | 2 |
| sb01 | Cities in Flight I | Thomas Galloway | |
| sb02 | Cities in Flight III | ?? | |
| rm27 | City / Country Diplomacy | Martin Janta-Polczynski | 7 |
| pw03 | City-State | Hartley Patterson | 7 |
| rm95 | Civilization Diplomacy | Babak Talebi | |
| ac17 | Classical Diplomacy | Andy Schwarz and Vincent Mous | 5 |
| rs44 | Classix | Martin Janta-Polczynski | 6 |
| ao01 | Claudian Diplomacy | Author Unknown | 5 |
| cn06 | Cline 9-Man Diplomacy I | R. Cline | 9 |
| cn01 | Cline 9-Man Diplomacy II (“IV”) | Robert Cline | 9 |
| cn04 | Cline 9-Man Diplomacy III | Robert Cline, Von Metzke, Naus and Bullock | 9 |
| cn05 | Cline 9-Man Diplomacy IV.1 (“V”) | Robert Cline and Fred Davis | 9 |
| cn09 | Cline 9-Man Diplomacy IV.2 | Conrad Von Metzke version of a Fred Davis revision | 9 |
| cn08 | Cline 9-Man Diplomacy V | Robert Cline, Fred Davis and Andrew Poole (for UKVB) | 9 |
| cn10 | Cline 9-Man Diplomacy VI | Robert Cline, Fred Davis, Andrew Poole, and David Rothery (First revision) | 9 |
| cn11 | Cline 9-Man Diplomacy VII | David Rothery’s Second Revision | 9 |
| cn12 | Cline 9-Man Diplomacy VIII | Robert Cline, Fred Davis, Simon Billenness and Mike Pustilnik | 9 |
| rm77 | Cluster Diplomacy | Steve Doubleday | 7 |
| rm03 | Coast-Running Variant | Eric Verheiden | 7 |
| rx25 | Code Duello | Glenn Overby | 5 |
| rb06 | Cognac | R. Bart | 7 |
| qp01 | Cold War | Rod Blacksaw | 5 |
| cs03 | Collapse of Classical Civilization, 400 A.D. (“4”) | | 4 |
| nu11 | Collapse of the Confederacy | S. William Nesbitt and Jim Cheaney | 7 |
| pa01 | Collapse of the Dual Empire | Richard Wein | 6 |
| gh01 | Colonia I | Fred Hyatt | 6 |
| gh04 | Colonia II | Fred Hyatt | 8 |
| gh05 | Colonia III | Fred Hyatt | 8 |
| gh06 | Colonia III-15 | Fred Hyatt and Robert Stimmel (requires gh05) | 15 |
| gh02 | Colonia IV | Fred Hyatt | 9 |
| gh03 | Colonia V | Fred Hyatt | 9 |
| gh09 | Colonia VI | Fred Hyatt | 9 |
| gh10 | Colonia VII | Fred Hyatt and John Cain (map is much reduced in size.) | 9 |
| gh14 | Colonia VIIb | Fred Hyatt and John Cain | 9 |
| gh11 | Colonia VIII (VII) | Fred Hyatt | 9 |
| np02 | Colonial America | Nick Danfort | 6 |
| ea04 | Colonial Diplomacy (Commercial Game) | P Hawes | 7 |
| uu04 | Colonial Variant | Glenn Reed and Peter Berggren | 7 |
| gh07 | Colonial Winters | Fred Winters | 17 |
| rw01 | Colonisation | Lew Pulsipher | |
| rw05 | Colonisation Diplomacy II | Michael Allaway | 8 |
| rp02 | Compilation of Simple Variants | Lew Pulsipher | 7 |
| rb52 | Completely Insane Diplomacy | Mick Haytack | 7 |
| rv01 | Complot | Evans Jones | |
| rs06 | Confewshun | David Staples | 7 |
| em16 | Conflict in the Middle East | William Nesbitt | 5 |
| od01 | Conquest of Australia | Bob Albrecht | 6 |
| ne03 | Conquest of North America | Anthony LeBoutillier | 7 |
| be01 | Conquest of the Land | Scott Rich | |
| wc01 | Conquest of the New World | Lew Pulsipher | |
| wc02 | Conquest of the New World II | Fred Davis | |
| wc03 | Conquest of the New World III | Fred Davis | |
| ls01 | Continent I | Andrew Phillips | 6 |
| ls03 | Continent II | Andrew Phillips and Fred Davis | 6 |
| cb57 | Contretemps (“II”) | Tom Swider | 7 |
| rb61 | Corner Diplomacy | Eric Brosius | 7 |
| sg16 | Cosmic Cluster | Glenn Overby | 7 |
| sg06 | Cosmic Diplomacy I | Larry Dunning | 7 |
| rg12 | Cosmic Diplomacy II | Russ Rusnak | 7 |
| en01 | Coup in Canberra | Andrew England | 5 |
| rn26 | Covert Diplomacy | Tom Dousette | 7 |
| rm70 | Crazy Whacko (CW) Heptadiplomacy | Mark Nelson | 7 |
| cm10 | Croatia Diplomacy | Larry Peery | 7 |
| rb84 | Crowded Diplomacy | Author Unknown | 11 |
| mc06 | Crusade 1200 | Tommy Larsson and John Pitre | 9 |
| mc04 | Crusadomacy | Gary Gygax | 7 |
| rb18 | Cryptodiplomacy I | John McCallum | 7 |
| rv11 | Cryptodiplomacy II | Glenn Overby | 7 |
| cc09 | Crystal Ball Diplomacy | Manus Hand & John Woolley | 7 |
| gf25 | Cthuloid Diplomacy | Tim Waterhouse and Gary Stevens | 7 |