Fluellen is a fictional character in the play Henry V by William Shakespeare. Fluellen is a Welsh captain, a leader of a contingent of troops in the small army of King Henry V of England while on campaign in France during the Hundred Years' War. He is a comic figure, whose characterisation draws on stereotypes of the Welsh at that time, but he is also portrayed as a loyal, brave and dedicated soldier.

The name 'Fluellen' is an anglicised version of the Welsh language Llywelyn. The Welsh sound [ɬ] does not exist in English, but is perceived by English speakers as similar to sequence fl. A similar process of anglicisation can be seen with Floyd for Llwyd (Lloyd being an alternative anglicisation retaining the double L, but changing the spelling of the vowel).

Shakespeare adheres to his seemingly common principle of portraying Welsh characters in his plays as basically comedic, offering the audience an opportunity to mock the manners, language, temperament and outmoded attitudes of their Celtic neighbours; compare with Glendower in Henry IV, Part 1 and Sir Hugh Evans the Welsh Parson in The Merry Wives of Windsor. All are wordy 'Welsh windbags' with amusing speech patterns and pronunciations, reactionary, overly sensitive and pedantic to a degree. Fluellen's obsession with proper military procedure epitomises this.

Fluellen does, however, have some 281 lines in Henry V. Neither a peripheral character nor merely comic in nature but a character well rounded, he affords humour but avoids buffoonery; generates great affection from the audience; and has poignancy, scope and dramatic range.

We see him first as a soldier, albeit driving rather than leading his men into the breach. This appearance comes after the bombastic "Once more unto the breach..." speech delivered by the King as he drives the comic stragglers Bardolph, Nym, Pistol and the Boy toward the enemy. Soon after, his character is fleshed out, with the emphasis on Fluellen's much mentioned "disciplines of the wars", with the first opportunity for a smirk at his accent, mannerisms and delivery (e.g., the Welsh "B" is far less voiced than the English "B", leading English hearers to half-mistake it for a "P", hence, "Alexander the Pig").

Lest there be underestimation of the Welshman's qualities as the play progresses, it is the King himself whom Shakespeare has deliver the words:

Though it appear a little out of fashion,
There is much care and valour in this Welshman.

By the end of the play, the audience comes to share the King's perspective. The affection for the character is secured by Fluellen's words after the miraculous victory at Agincourt, when the French herald, Montjoy, comes to cede for peace. Fluellen's relief and joy bursts out in his exchange with the King who says (with reference to his own birth in Monmouth) "I am Welsh, you know, good countryman" leading to Fluellen's tearful "By Jeshu, I am your majesty's countryman, I care not who know it; I will confess it to all the 'orld: I need not to be ashamed of your majesty, praised be God, so long as your majesty is an honest man."