Britannia is a British historical fantasy drama^[3] television series created by Jez Butterworth and Tom Butterworth.^[4] The show was the first co-production between Sky UK and Amazon Prime Video and stars Kelly Reilly, David Morrissey, Zoë Wanamaker, Mackenzie Crook, Nikolaj Lie Kaas, and Eleanor Worthington Cox.^[5] It first aired on Sky Atlantic in the UK beginning 18 January 2018 and on Amazon Prime Video in the US beginning 26 January 2018.^[6] The first series aired on Epix beginning 2 August 2020.^[7] Pop songs were used as theme music for the three series to date: Donovan's "Hurdy Gurdy Man" (series 1), his "Season of the Witch" (series 2), and "Children of the Revolution" by T. Rex (series 3). In March 2023, the series was cancelled after three seasons.^[8]

Britannia is set in 43 AD, when the Romans invaded Britain. Julius Caesar had failed to conquer Britain 90 years earlier.

General Aulus Plautius and his second-in-command, Lucius are determined to succeed where Julius Caesar failed, by any means necessary. An experienced warrior, Aulus establishes a fortified camp, gathers information from captives, even children, and learns that the Druids are the driving force behind the many tribes he faces. He determines that "you don't conquer the people, you must conquer their gods." He meets the Druids and undertakes a vision quest. Soon, he is talking aloud to Lokka, a demon king.

Young Cait of the Cantii tribe is about to take part in a ceremony to mark her becoming an adult woman when the Romans attack and largely destroy her tribe. She is forced to flee and wanders the forest, where she encounters and attaches herself to an unlikely protector, Divis "The Outcast".

Divis is a Druid with some mystical powers—divination, hypnosis, visions—but seems mad and has been driven into exile by Veran, leader of the Druids in Britannia. Divis roams the countryside seeking clues to the meaning of his apocalyptic visions, and believes he is on some kind of mysterious "mission".

Kerra, a princess as the daughter of the Cantii King Pellenor, frets for her people's safety. The Cantii are in a perpetual feud with the Regni, a powerful and large tribe. The Cantii's only protection is an impregnable natural fortress formed from granite. Yet, King Pellenor makes no preparations to resist the Romans, other than relying on vague hints from the Druids to set policy. Kerra's brother, Phelan, appears weak. Kerra ambitiously takes her own steps to address the Roman threat, calling for a parley and venturing into Regni territory. Her actions enrage her father, who sends her to be judged by the Druids, and possibly flayed alive, as happened to her mother.

In the maelstrom of confusion and fear caused by the invasion, Romans and Britons ally with, and betray, each other as the Romans consolidate their position and disaster looms.

The first series was produced by Rick McCallum, Vertigo Films and Neal Street Productions and shot on location in Czech Republic and Wales.^[13] Most dialogue in the series is spoken in English, which is used mostly to represent Vulgar Latin spoken by the Romans and Brythonic spoken by the Celts. Latin and Welsh (with English subtitles) are also used to represent both ancient languages, respectively,^{[citation needed]} particularly in rituals and other scenes with formulaic language.

In March 2018, it was announced that Sky Atlantic had renewed the show for a second series.^[14] Amazon was not involved in production and did not stream the second season.^[15]

The show was renewed for a third series in January 2020.^[15] In June 2020, U.S. premium network Epix announced it would partner with Sky to produce the third series. It would also air the first series beginning August 2, 2020, and the second series beginning October 4, 2020.^[7] Filming of the third series was shut down in March 2020 due to the Coronavirus pandemic,^[16] and resumed in September 2020.^[17][18]

Season 2 began streaming on Amazon Prime in June 2021.^[19]

This section needs expansion. You can help by adding to it. (February 2018)

The first season received positive reviews. The review aggregator website Rotten Tomatoes reported a 76% approval rating, with an average rating of 6.54/10 based on 37 reviews, with site's critics consensus saying:

"Brilliantly bonkers, Britannia's duplicitous characters and campy fantasy won't be for everyone, but those looking for less-serious swords and sorcery may enjoy its spellbinding madness."^[20]

On Metacritic, which uses a weighted average, the first season scored 70 out of 100, based on eight reviews, indicating "generally favorable reviews".^[21]