Bigthan and Teresh were two eunuchs in service of the Persian king Ahasuerus, according to the Book of Esther. Mordecai rested in the courtyard one day and overheard these two eunuchs plotting to kill the king. He went on to inform the king through Esther, thus thwarting the plot. He was rewarded by the king afterwards.
According to the deuterocanonical/apocryphal Additions to the Book of Esther available in the Greek Septuagint translation of the Bible, they are known as Gabatha and Tharra (Koine Greek: Γαβαθά καὶ Θαρρα). Bigthan's name is also spelled "Bigtan" or "Bigthana". It is a Persian name which means "Gift of God".