First dictionaries of the English language
The early modern period was an era of great change for the English language. The number of words ‘available’ to speakers of English more than doubled between 1500 and 1650. Many of the new words were borrowed into English from the Latin or Greek of the Renaissance must have seemed hard to understand to many of the population.
A Dictionary of the English Language published on 15 April 1755 and written by Samuel Johnson
Johnson's dictionary was not the first English dictionary. Over the previous 150 years more than twenty dictionaries had been published in England, the oldest of these being a Latin-English "wordbook" by Sir Thomas Elyot published in 1538.
If you don't want to count the Wordbook of Elyot because it's Latin - English (rather than just English), then there is a purely English dictionary published by Richard Mulcaster in 1583
John Florio published an Italian - English dictionary in 1598 that was the first to give definitions for the meanings of the words.
Dictionary by Cawdrey 1604
A table alphabetical (1604) is generally regarded as the first genuine dictionary in English by Robert Cawdrey
Thomas Blount's Glossographia, or, A dictionary interpreting all such hard words, of whatsoever language, now used in our refined English tongue (1656)
The New World of English Words Or A General Dictionary (1658)