In which play is the line 'Lord, what fools these mortals be!' spoken?

“Lord, what fools these mortals be!” is spoken in A Midsummer Night’s Dream.

The speaker is Puck, also called Robin Goodfellow, a mischievous fairy serving Oberon, the fairy king. Puck says the line in Act III, Scene 2, while observing the tangled romantic confusion caused by magic in the woods near Athens.

Puck has mistakenly enchanted Lysander with a love potion intended for Demetrius. After Oberon orders the mistake corrected, Puck watches as the mortal lovers quarrel, pursue the wrong partners, and become increasingly bewildered. His comment captures the play’s comic view of human love: intense, changeable, and easily manipulated by appearances or enchantment.

The line is sometimes misattributed to Oberon because both characters are present in the scene, but the text identifies Robin as the speaker. Puck’s role also connects the fairy plot to the play-within-a-play performed by the mechanicals, whose own confusion and theatrical incompetence provide another comic portrait of mortal foolishness.