Pigweed can mean any of a number of weedy plants which may be used as pig fodder:

• Amaranthus species
  • Amaranthus albus, white pigweed, tumble pigweed
  • Amaranthus blitoides, prostrate pigweed
  • Amaranthus californicus, California pigweed
  • Amaranthus fimbriatus, fringed pigweed
  • Amaranthus hybridus, smooth pigweed
  • Amaranthus palmeri, the 'pigweed' resistant to glyphosate in the US Southeast
  • Amaranthus retroflexus, redroot pigweed
• Chenopodium album white goosefoot
• Polygonum aviculare
• Portulaca species