Ľ/ľ is a grapheme found only in the Slovak alphabet. It is an L with a caron diacritical mark, more normally ˇ but simplified to look like an apostrophe with L, and is pronounced as palatal lateral approximant [ʎ], similar to the "lj-" sound in Ljubljana or million.
Examples:
Note that an approximation using an ' apostrophe is sometimes found in some English texts, for example "L'udovit Stur" (sic) for correct Slovak Ľ-caron in Ľudovít Štúr (1812-1856). This incorrect usage is sometimes the result of an OCR error.
References
Ľ Wikipedia(Text) CC BY-SA