Synonyms of perfidious

perfidious

adjective

(ˌ)pər-ˈfi-dē-əs 

as in traitorous

not true in one's allegiance to someone or something

a perfidious campaign worker revealed the senator's strategy to his leading rival for the nomination

Synonyms & Similar Words

• traitorous
• false
• treacherous
• unreliable
• disloyal
• faithless
• unfaithful
• untrue
• inconstant
• fickle
• recreant
• irresponsible
• untrustworthy
• hesitant
• uncertain
• undependable
• dubious
• faltering
• irresolute
• trustless
• uninterested
• dispassionate
• vacillating
• apathetic
• wavering

Antonyms & Near Antonyms

• true
• faithful
• constant
• loyal
• devout
• steadfast
• responsible
• staunch
• steady
• reliable
• devoted
• dedicated
• fast
• dutiful
• solid
• trustworthy
• dependable
• down-the-line
• trusty
• unfaltering
• unhesitating
• resolute
• tried
• intent
• inveterate
• determined
• confirmed
• enthusiastic
• tried-and-true
• ardent
• passionate
• fervent
• trustable
• impassioned
• unwavering
• fervid
• sworn
• avid
• dyed-in-the-wool

Synonym Chooser

How is the word perfidious different from other adjectives like it?

Some common synonyms of perfidious are disloyal, faithless, false, traitorous, and treacherous. While all these words mean "untrue to what should command one's fidelity or allegiance," perfidious adds to faithless the implication of an incapacity for fidelity or reliability.

a perfidious double-crosser

When can disloyal be used instead of perfidious?

The words disloyal and perfidious are synonyms, but do differ in nuance. Specifically, disloyal implies a lack of complete faithfulness to a friend, cause, leader, or country.

disloyal to their country

Where would faithless be a reasonable alternative to perfidious?

The meanings of faithless and perfidious largely overlap; however, faithless applies to any failure to keep a promise or pledge or any breach of allegiance or loyalty.

faithless allies

When is false a more appropriate choice than perfidious?

The words false and perfidious can be used in similar contexts, but false stresses the fact of failing to be true in any manner ranging from fickleness to cold treachery.

betrayed by false friends

In what contexts can traitorous take the place of perfidious?

Although the words traitorous and perfidious have much in common, traitorous implies either actual treason or a serious betrayal of trust.

traitorous acts punishable by death

When could treacherous be used to replace perfidious?

While in some cases nearly identical to perfidious, treacherous implies readiness to betray trust or confidence.

a treacherous adviser

Example Sentences

Recent Examples of perfidious

Observing human behavior confirms that for some among us, the perfidious lust for unbridled power and the imposition of cruelty in its quest know no bounds and are bereft of human decency. —A.o. Scott, New York Times, 3 Feb. 2026

This perfidious situation, unintentional as its creation may have been, was strongly critiqued as far back as 1983 by Jonathan Crush and Paul Wellings in an article in The Journal of Modern African Studies. —The Editors, JSTOR Daily, 15 Aug. 2025

Those voting for it are Sean Elo-Rivera, Jennifer Campbell, Kent Lee, Stephen Whitburn, Vivian Moreno and La Jolla’s own Joe LaCava, who has been an active supporter of this perfidious plan. —Inga, San Diego Union-Tribune, 16 June 2025

The regime’s propaganda inspires fear of dire threats from predatory Japanese and perfidious Americans, who are aided by traitorous South Koreans. —Jennifer Lind, Foreign Affairs, 25 Oct. 2010

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