Critical Role (sometimes abbreviated as CR) is an American actual play web series in which a group of professional voice actors play Dungeons & Dragons. The principal cast consists of Matthew Mercer, Ashley Johnson, Travis Willingham, Laura Bailey, Liam O'Brien, Taliesin Jaffe, Marisha Ray, Orion Acaba, Sam Riegel, Robbie Daymond, Aabria Iyengar, Brennan Lee Mulligan, Luis Carazo, Whitney Moore and Alexander Ward.

There have been three campaigns set in world of Exandria – Campaign 1 which ran from March 2015 to October 2017, Campaign 2 which ran from January 2018 to June 2021, and Campaign 3 which ran from October 2021 to February 2025. While the first three campaigns are set in the same shared world, each follows a different set of characters created and played by the principal cast. However, Campaign 3 saw the return of Sir Bertrand Bell for the first three episodes. Bell was a character previously seen in The Search for Grog and The Search for Bob, which are in medias res wrap-up specials for Campaign 1. Bell is played by Willingham in each instance. Campaign 3 also has characters crossing over from the spinoff anthology series Exandria Unlimited (ExU); with Johnson starring as Fearne Calloway, and O'Brien as Orym of the Air Ashari. Fellow ExU cast member Robbie Daymond also guest stars as Dorian Storm throughout the campaign. Additionally, a number of player characters from earlier campaigns cameo as non-player characters (NPCs) played by Mercer in Campaign 3. Towards the end of Campaign 3, the players reprise their Campaign 1 and 2 characters for short arcs.

Campaign 4, which premiered in October 2025, is set in a new world, Aramán. It features an expansion of the main cast to 13 players and Mulligan taking over Mercer's place as Dungeon Master.

This section includes characters who will appear or have appeared in each season.

For the first 27 episodes of Campaign 1 there were nine cast members: eight players and a Dungeon Master. This became eight from episode 28, when Orion Acaba left the show, and continued through the third campaign. The cast was then expanded to 13 players and one Dungeon Master with the fourth campaign; it was the first Critical Role campaign to use a West Marches-style structure.

Mercer is Critical Role's primary Dungeon Master (DM). As the DM, Mercer organizes the gameplay, describes the effects the player characters' actions have on the world and narrative, and plays the non-player characters (NPCs). In Campaign 3, during Aabria Iyengar's stint as a guest DM, Mercer plays Dariax Zaveon—his Exandria Unlimited character. Mercer is absent during the Campaign 3's special, Critical Role: Downfall—a three part special, airing mid-way through Campaign 3 and helmed by Brennan Lee Mulligan.

Academics Zac Boyd and Míša Hejná, in the journal Language in Society, highlighted that Mercer "introduced 1,144 unique NPC characters during" the second campaign . They analyzed nineteen characters based on exceeding a threshold of minimum voice time and plot relevance and determined through "holistic analysis of voice quality" of these characters that "breathiness" in Mercer's voice "emerged as signalling positive morality and stances of safety, comfort, and trust, where whisperiness signals negative morality and stances of threat. Qualitatively, pitch dynamism was also found to correlate with morality and stancetaking: the more limited the pitch dynamism, the more likely it is that the character portrayed is an Enemy and that they adopt stances of threat". Academics Jens Kjeldgaard-Christiansen, Boyd, Hejná, and Mark Ølholm Eaton, in the Journal of Language and Pop Culture, then conducted a study involving 250 participants who assessed the perceived moral traits of 22 fictional characters, created and voiced by Mercer during the second campaign, after listening to short audio samples of their voices without narrative context. They noted that participants heard "protagonists and other morally positive characters" and "antagonists and other morally negative characters" as such; the main exception is that "subversively evil characters [...] were perceived as morally neutral, even trending toward good", which authors felt made sense as these characters are trying to hide their intentions. They highlighted that while the "participants had very different degrees of experience with Critical Role" from familiarity to no familiarity, the study showed "their moral perceptions of particular character voices were nevertheless remarkably consistent, and so were the perceptions of participants with different region/language backgrounds. These consistencies indicate that, rather than being peculiar to the voice actor or endemic to the fictional context of Critical Role, the vocal cues to which our participants responded may reflect culturally widespread and psychologically deep-seated forms of moral rhetoric that resound through different fictional contexts".

Academic Malene Brix Ley, in the Journal of Language Works, analyzed the voices of twenty allies and antagonists selected from the first three campaigns to investigate Mercer's use of linguistic profiling. Ley argued that "that Mercer does not use accents to differentiate between antagonists and allies" and while his antagonists have some linguistic profiling through his use of Standard British English (SBE), "the balanced distribution of allies' accents prevents players from associating any single accent with an ally" and Mercer's characters are "linguistically nuanced". She stated that Mercer uses specific accents that include "recognisable stereotypes" for the players; however, the "data indicates" Mercer uses "a range of standard and non-standard accents" to avoid "rigid moral associations" and "accents that could be perceived as appropriation or discrimination". While allied characters had a higher variation in accent distribution, antagonists predominantly had SBE accents; Ley noted that "Mercer also uses features associated with Upper-Crust [Received Pronunciation (RP)]" which is "linked with the British upper class". Antagonists Delilah and Sylas Briarwood, Trent Ikithon, and Ira Wendagot "embody stereotypical villainous traits", "all are manipulative and self-serving", and three are wizards – Ley commented that "this reinforces the association of SBE with negative qualities, particularly the stereotype of the intellectual yet malicious 'evil geniuses' [...]. Mercer's use of features from Upper-Crust RP further underscores these stereotypes and indexes their higher social status and authority". Kjeldgaard-Christiansen et al. highlighted Ley's study, and also noted the lack of moral consistency with Mercer's accents outside the use of SBE. The respondents in their study perceived the "most immoral" characters based on the "their exceptional voice qualities" rather than "their particular accents".