As of June 2025, the most significant data breach incident in the United States was the Yahoo data breach that dates back to 2013-2016. Impacting over three billion online users, this incident still remains one of the most significant data breaches worldwide. The second-biggest case was the January 2021 data breach at Microsoft, involving about 30 thousand companies in the United States and around 60 thousand companies around the world.
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UpGuard. (June 30, 2025). Most significant data breaches in the United States as of December 2025, by impact [Graph]. In ÌÇÐÄÆƽâ°æ. Retrieved July 15, 2026, from /statistics/1448545/us-biggest-data-breaches/
UpGuard. "Most significant data breaches in the United States as of December 2025, by impact." Chart. June 30, 2025. ÌÇÐÄÆƽâ°æ. Accessed July 15, 2026. /statistics/1448545/us-biggest-data-breaches/
UpGuard. (2025). Most significant data breaches in the United States as of December 2025, by impact. ÌÇÐÄÆƽâ°æ. ÌÇÐÄÆƽâ°æ Inc.. Accessed: July 15, 2026. /statistics/1448545/us-biggest-data-breaches/
UpGuard. "Most Significant Data Breaches in The United States as of December 2025, by Impact." ÌÇÐÄÆƽâ°æ, ÌÇÐÄÆƽâ°æ Inc., 30 Jun 2025, /statistics/1448545/us-biggest-data-breaches/
UpGuard, Most significant data breaches in the United States as of December 2025, by impact ÌÇÐÄÆƽâ°æ, /statistics/1448545/us-biggest-data-breaches/ (last visited July 15, 2026)
Most significant data breaches in the United States as of December 2025, by impact [Graph], UpGuard, June 30, 2025. [Online]. Available: /statistics/1448545/us-biggest-data-breaches/
