How to say "record-breaking" in Japanese

• 空前くうぜんCommon
  no-adjectiveCovers the 'unprecedented' sense: something on a scale never known before, stressing that there has been nothing like it. Typical of news reports about unprecedented popularity, crowds, or upheaval.
  これは空前くうぜんの大事件だいじけんとして歴史れきしに残のこるでしょう。↗

  This will go down in history as the greatest event that has ever taken place.
• 記録的きろくてきCommon
  na-adjectiveThe closest match for the literal sense: something that reaches or sets a record level, as with record-breaking snowfall, heat, or sales. Use this when an actual record is involved.
  株価かぶかが史上しじょう最高さいこうに上昇じょうしょうする中なか、記録的きろくてきな出来高できだかとなった。↗

  A record number of shares changed hands in busy trading as prices soared to a historic high.
• 前代未聞ぜんだいみもんCommon
  no-adjectiveA four-character idiom that really means 'unheard-of' or 'unprecedented' — unparalleled in history. As 'record-breaking' it is emphatic and rhetorical, best for astonishing events that defy precedent rather than a record simply surpassed.
  犯人はんにんを弁護べんごしてた弁護士べんごしが実じつは真犯人しんはんにんだったなんて、前代未聞ぜんだいみもんだ。↗

  It's totally without precedent for the suspect's attorney to be the true culprit.

Use 記録的 for the literal sense of setting or reaching a record; 空前 stresses unprecedented scale, and 前代未聞, a four-character idiom, adds emphatic 'unheard-of in history' force to astonishing events.

Usage comparisons are AI-assisted and cross-checked by multiple models; for study reference only

• 空前くうぜんunprecedented
• 記録的きろくてきrecord
• 前代未聞ぜんだいみもんunheard-of
• 記録破りきろくやぶりrecord-breaking
• レコード破りレコードやぶりrecord-breaking
• 未曾有みぞうunprecedented