Mythomania

: an excessive or abnormal propensity for lying and exaggerating

Example sentence:
The therapist speculated that Sharon's mythomania, which makes her want to embellish even the most minor details of her life, may have been triggered by a specific event.

Did you know?

We wouldn't lie to you about the history of "mythomania." It comes from two ancient roots, the Greek "mythos" (meaning "myth") and the Late Latin "mania" (meaning "insanity marked by uncontrolled emotion or excitement"). One myth about "mythomania" is that it's a very old word; actually, the earliest known uses of the term date only from the beginning of the 20th century. It was predated by a related word, "mythomaniac," which appeared around the middle of the 19th century. "Mythomaniac" initially referred to someone who was obsessed with or passionate about myths but was eventually used for individuals affected with or exhibiting mythomania.