Step 1: The famous line "A thing of beauty is a joy forever" is from John Keats' poem Endymion.
Step 2: It reflects Keats' romantic philosophy that beauty transcends time. \[ \boxed{\text{John Keats}} \]
Match the quoted line and its poetic style to the correct poet among the options.
The line is specifically the opening of Keats' Endymion.
So, the correct answer is John Keats.