千分比（per mil或per mill，符号为‰ ，Unicode：U+2030）是一种表达比例、比率或分数数值的方法，使用1000作为分母。

例如：

千分比的英文名称是permil、permille、per mil、per mill或promille。

A per mille (from Latin per mīlle, "in each thousand"), also spelled per mil, per mill, permil, permill, or permille is a sign indicating parts per thousand. Per mil should not be confused with parts per million (ppm).

The sign is written ‰, which looks like a percent sign (%) with an extra zero in the divisor. It is included in the General Punctuation block of Unicode characters: U+2030‰PER MILLE SIGN (HTML ‰ ·‰). It is accessible in Windows using ALT+0137.