The 18-line poem was discovered 30 years ago by two U.S. scholars researching a manuscript notebook kept by an Elizabethan courtier named Henry Sanford. The poem was included in a new edition of Shakespeare's works published this month, The Daily Mail reported.
"Some people believe it is by Shakespeare, some people do not," said Jonathan Bate, the University of Warwick professor who edited the Shakespeare collection. "I am now 99 per cent certain it was written by Shakespeare."
Bate said he believes the poem was an epilogue added to "As You Like It" for a court performance on Shrove Tuesday in 1599. He said lines written especially for the occasion were a requirement for performances before the queen.
"Shakespeare was probably in the habit of dashing some lines down on the back of an envelope and then chucking them away," he said. "By chance, this one example has survived."