Weakness or asthenia is a symptom of a number of different conditions.

Weakness may also refer to:

• Muscle weakness, the inability to exert force with one's muscles
• The Weakness, the thirty-seventh book in the Animorphs series
• "Weakness", a song by Opeth from Damnation
• "Weakness", a song by The Wanted from The Wanted
• The Weakness (album), 2023 album by Ruston Kelly

• All pages with titles containing weakness
• All pages with titles beginning with weakness
• Weak (disambiguation)
• Akrasia, also known as "weakness of will"
• Drawback (disambiguation)
• Facial weakness
• Fatigue (medical)
• Somnolence
• Strength (disambiguation)
• Vulnerability