Monolene, the deepwater lefteye flounders, is a genus of small, mainly deepwater flatfish from the Atlantic and East Pacific.

Their eyes are located on the left side of their body, and thus they have long been placed in the "lefteye flounder" family, Bothidae. However, more recent studies have split up the family into multiple families, with Monolene being identified as the sister group to the family Taeniopsettidae (formerly the subfamily Taeniopsettinae). For this reason, it was placed its own family, Monolenidae, in 2025.

...