22 Japanese ways to say “Swear to god”

Swearing to God is a powerful way to show sincerity, frustration, or strong emotion in English. But how do you say that in Japanese without sounding strange or overly formal?

Japanese has a ton of ways to express this feeling, from casual slang to heartfelt promises. And because of cultural nuances, some expressions are stronger or softer than others.

This list of 22 Japanese phrases will help you swear to God in style, matching your mood and situation. Whether you want to sound casual, respectful, or native-like, there’s something here for you.

Let’s dive in and discover how Japanese speakers swear to God—without actually invoking a deity every time!

By learning these, you’ll not only sound more natural but also understand the emotion behind the words better.

Ready? Let’s get started with some casual expressions!

Getting Started: What Does “Swear to God” Mean in Japanese?

In Japanese, swearing to God isn’t always literal. Instead, people use phrases that strongly affirm their honesty or feelings.

Many expressions come from Buddhist or Shinto influence, or just everyday slang. Understanding context is key because some phrases are casual, others formal, and a few are just native slang.

Starting with these basics will help you grasp the nuances before moving to more colorful expressions.

Sometimes, using a great beginner phrasebook can give you a perfect starting point for a cohesive understanding.

With practice, you’ll be able to pick the right phrase for the right moment.

Let’s see some casual suggestions first.

Part 1: Casual Suggestions

1. 神様に誓う (Kamisama ni chikau) – “I swear to God.”

This is the most direct way to say “I swear to God” in Japanese.

神様 (Kamisama) means “God,” and 誓う (chikau) means “to swear” or “to vow.” It’s straightforward and works well when you want to be serious but not too formal.

Use this when you want to emphasize honesty or a promise.

It’s a strong phrase but still casual enough for friends or family.

Related phrase: 本当に神様に誓う (Hontō ni kamisama ni chikau) means “I really swear to God.”

Try it next time you want to stress your sincerity—it’s a classic!

2. マジで (Maji de) – “Seriously” / “For real.”

マジで is casual slang meaning “seriously” or “for real.”

It’s a great way to swear by your word without sounding formal or religious.

Use it in daily conversations to emphasize that you’re telling the truth.

It’s super common among young people, so it’s great for casual chats.

Just be aware that it’s very informal and not fit for business or formal situations.

Example: マジで信じてる (Maji de shinjiteru) means “I seriously believe it.”

3. 本気で (Honki de) – “Honestly” / “Seriously.”

本気 (Honki) means “seriousness” or “earnestness.” Adding で makes it an adverb.

This phrase is slightly more neutral and can fit semi-formal situations.

Saying 本気で can convey you mean what you say deeply and honestly.

It’s perfect when you want to be clear without being too casual or overly formal.

For example, 本気で言ってる (Honki de itteru) means “I’m seriously saying it.”

Use it when you want to sound sincere but not too intense.

4. 神に誓って (Kami ni chikatte) – “Swearing by God.”

Similar to 神様に誓う, this phrase means “I swear by God.”

神 (Kami) is a more general word for “god” or “deity,” and 誓って (chikatte) is the te-form of “to swear.”

It’s a slightly more poetic way to swear something truthful.

People often use it in dramatic or serious moments.

Example: 神に誓って嘘じゃない (Kami ni chikatte uso janai) means “I swear by God, it’s not a lie.”

Use it to add some emotional weight.

5. 約束するよ (Yakusoku suru yo) – “I promise.”

約束 (Yakusoku) means “promise,” so this phrase is a straightforward “I promise.”

While not literally swearing to God, it’s a common way to assure someone of your honesty or commitment.

It’s neutral and polite enough for many situations.

Adding よ (yo) at the end adds emphasis and friendliness.

Example: 絶対に約束するよ (Zettai ni yakusoku suru yo) means “I absolutely promise.”

This is perfect when you want to sound reliable without religious overtones.

6. 嘘じゃないってば！(Uso janai tte ba!) – “I’m not lying, seriously!”

嘘じゃない (Uso janai) means “not a lie,” and ってば adds an emphatic, slightly pleading tone.

This phrase is perfect for casual situations when you want to strongly assert honesty.

It’s very conversational and natural.

Great for friends or informal chats.

Just be careful not to overuse or sound defensive.

Example: 本当に嘘じゃないってば！(Hontō ni uso janai tte ba!) means “I really am not lying!”

7. 信じて！(Shinjite!) – “Believe me!”

信じて is the imperative form of 信じる (shinjiru), “to believe.”

This short phrase is an emotional plea: “Believe me!”

It’s simple and effective to convey your honesty.

Often used when people doubt you and you want to convince them.

It’s informal but can be heartfelt.

Example: 私の言うことを信じて！(Watashi no iu koto o shinjite!) means “Believe what I say!”

8. マジで言ってる (Maji de itteru) – “I’m seriously saying it.”

This phrase combines マジで (“seriously”) with 言ってる (itteru), “I’m saying.”

It’s a natural, casual way to insist you mean what you say.

Very common among younger people and in informal settings.

It’s like saying “No joke, I’m serious.”

Example: マジで言ってる、嘘じゃないよ！(Maji de itteru, uso janai yo!) means “I’m seriously saying this, not lying!”

Use it to sound genuine and casual.

Part 2: Polite & Formal Suggestions

9. 本当に申し上げます (Hontō ni mōshiagemasu) – “I truly swear.”

This phrase is formal and respectful.

申し上げます (mōshiagemasu) is a humble way to say “say” or “tell,” and 本当に means “truly.”

Use this when you want to swear or affirm something seriously in formal settings.

It’s perfect for business or official promises.

Example: 本当に申し上げます、これは真実です (Hontō ni mōshiagemasu, kore wa shinjitsu desu) means “I truly swear, this is the truth.”

This phrase elevates your sincerity with politeness.

10. 確かに誓います (Tashika ni chikaimasu) – “I certainly swear.”

確かに (Tashika ni) means “certainly” or “surely,” and 誓います (chikaimasu) is the polite form of “to swear.”

It’s a formal, confident phrase used in business or serious situations.

It’s less casual and carries weight.

Example: 確かに誓います、責任を持ちます (Tashika ni chikaimasu, sekinin o mochimasu) means “I certainly swear, I will take responsibility.”

Great for promises that matter deeply.

11. 心から誓います (Kokoro kara chikaimasu) – “I swear from my heart.”

This phrase emphasizes sincerity with 心から (kokoro kara), meaning “from the heart.”

It’s polite and emotionally strong.

Use it to show deep honesty or heartfelt promises.

Example: 心から誓います、あなたを助けます (Kokoro kara chikaimasu, anata o tasukemasu) means “I swear from my heart, I will help you.”

Perfect for emotional or serious commitments.

12. 誓いを立てます (Chikai o tatemasu) – “I make a vow.”

誓い (chikai) means “vow” or “oath,” and 立てます (tatemasu) means “to make” or “establish.”

It’s a formal way to say you’re swearing to something important.

Often used in official or ceremonial contexts.

Example: 私は誓いを立てます、正直に生きます (Watashi wa chikai o tatemasu, shōjiki ni ikimasu) means “I make a vow to live honestly.”

Good for serious promises or commitments.

13. 誠に誓います (Makoto ni chikaimasu) – “I sincerely swear.”

誠に (Makoto ni) means “sincerely,” paired with the polite 誓います (chikaimasu) for “swear.”

This phrase is very respectful and sincere.

It’s great for formal speech or written statements.

Example: 誠に誓います、最善を尽くします (Makoto ni chikaimasu, saizen o tsukushimasu) means “I sincerely swear to do my best.”

Use it when you want to sound trustworthy and serious.

14. 神の名において誓います (Kami no na ni oite chikaimasu) – “I swear in the name of God.”

This is a very formal and somewhat religious phrase.

神の名において means “in the name of God,” used in solemn vows.

It’s rarely used in casual speech but can appear in ceremonial or dramatic contexts.

Example: 神の名において誓います、嘘ではありません (Kami no na ni oite chikaimasu, uso de wa arimasen) means “I swear in the name of God, I’m not lying.”

Use with caution and respect.

15. 約束いたします (Yakusoku itashimasu) – “I humbly promise.”

約束いたします is a very polite, humble way of saying “I promise.”

It’s appropriate in business or formal settings.

While not a direct “swear to God,” it functions similarly to affirm trustworthiness.

Example: 必ず約束いたします (Kanarazu yakusoku itashimasu) means “I will definitely promise.”

Use this to sound respectful and reliable.

16. 真実を誓います (Shinjitsu o chikaimasu) – “I swear the truth.”

真実 (shinjitsu) means “truth,” and 誓います (chikaimasu) means “I swear.”

This phrase is a formal declaration of honesty.

It works well in serious conversations or statements.

Example: 真実を誓います、嘘はありません (Shinjitsu o chikaimasu, uso wa arimasen) means “I swear the truth, there is no lie.”

Use it when you want to be crystal clear about honesty.

Part 3: Very Casual / Native-like Expressions

17. ガチで (Gachi de) – “For real” / “No joke.”

ガチで is slang for “seriously” or “for real.”

It’s very casual and common among youth.

Use it to swear by your word in a native-sounding way.

Example: ガチで言ってる！(Gachi de itteru!) means “I’m seriously saying this!”

Perfect for emphasizing truth in casual talk.

Keep in mind, it’s informal and not for official use.

18. まじ卍 (Maji manji) – “Seriously, no joke.”

まじ (Maji) means “seriously,” and 卍 (manji) is a trendy symbol used in youth slang to emphasize something.

Together, まじ卍 is a fun, casual way to say “no kidding” or “seriously.”

It’s very native and youthful.

Example: まじ卍で嘘じゃない！(Maji manji de uso janai!) means “Seriously, no lie!”

Use this to sound hip and casual—but only with close friends.

19. 嘘やん！(Uso yan!) – “No way!” / “You’re lying!”

嘘やん is a Kansai dialect phrase meaning “That’s a lie!” or “No way!”

It’s casual and sometimes playful.

Use it when surprised or doubting something.

Example: 嘘やん、マジで？(Uso yan, maji de?) means “No way, seriously?”

Great for native-like conversations in informal settings.

20. ほんまに (Honmani) – “Really” (Kansai dialect)

ほんまに is the Kansai dialect version of 本当に (hontō ni), meaning “really.”

It’s casual and very commonly used in western Japan.

Use it to swear honestly in a friendly way.

Example: ほんまに言うてるで！(Honmani iuteru de!) means “I’m really saying it!”

Add some local flavor to your Japanese with this one.

21. 嘘や！(Uso ya!) – “No lie!” (Kansai dialect)

Another Kansai dialect phrase, 嘘や means “No lie!”

It’s energetic and casual, perfect for expressing surprise or honesty.

Example: 嘘や、ほんまやで！(Uso ya, honma ya de!) means “No lie, it’s true!”

A fun way to sound native if you want to try dialects.

22. めっちゃマジ (Meccha maji) – “Super serious.”

めっちゃ means “very” or “super,” combined with マジ (“serious”), it means “super serious.”

This phrase is casual, trendy, and perfect for swearing your word emphatically.

Example: めっちゃマジで言ってる！(Meccha maji de itteru!) means “I’m super serious!”

Use it to add energy and sincerity in casual talk.

It’s a great phrase to sound natural and lively.

Concluding Thought

Exploring these 22 Japanese ways to say “Swear to God” opens up a world of expression beyond literal translations.

From formal vows to casual slang, each phrase carries unique cultural and emotional weight, helping you connect with native speakers on a deeper level.

Keep practicing, and don’t be afraid to use these phrases in everyday conversations to sound more natural and sincere. You’ve got this!