There are many mentions of plagues in the Bible. The most prominent are those mentioned during Moses time in Egypt and in the book of Revelation.
The Pharaohs of Ancient Egypt did not listen to Moses or Aaron when they were told they should not worship their false gods. They also kept the Lord's chosen people as slaves. Because of this, God sent ten plages to Egypt: the first plague turned water into blood, the second plague made frogs miraculously appear, the third plague was swarms of gnats, the fourth plague was swarms of flies, the fifth plague made livestock diseased, the sixth plague gave the people boils, the seventh plague was hail storms, the eighth plague brought swarms of locusts, the ninth plague created darkness over the land and the tenth plague killed the firstborn of families (except for those that were passed over).
These were the most well known plagues mentioned in the Bible, but the book of Revelation also features plagues that will come at the end of days.