This is a list of the flora of Nihoa, an island in the Northwestern Hawaiian Islands, part of the City & County of Honolulu in the U.S. state of Hawaii. Nihoa is listed in the National Register of Historic Places and protected under the Papahānaumokuākea Marine National Monument.
| Species | Common name | Status | |
|---|---|---|---|
| Nephrolepis multiflora | Sword fern | Naturalized alien | |
| Pritchardia remota | Loulu | Endemic | |
| Cenchrus echinatus | Sandbur | Naturalized alien | |
| Eragrostis variabilis | ʻEmo-loa | Indigenous | |
| Panicum torridum | Kākonakona | Indigenous | |
| Paspalum sp. | Naturalized alien | ||
| Setaria verticillata | Bristly foxtail | Naturalized alien | |
| Tetragonia tetragonoides | New Zealand spinach | Naturalized alien | |
| Amaranthus brownii | Endemic | ||
| Heliotropium curassavicum | Nena | Indigenous | |
| Schiedea verticillata | Nihoa carnation | Endemic | |
| Chenopodium oahuense | ʻAweoweo | Indigenous | |
| Ipomoea indica | Koaliʻawahia | Indigenous | |
| Ipomoea pes-caprae | Beach morning glory | Indigenous | |
| Sicyos pachycarpus | ʻĀnunu | Indigenous | |
| Euphorbia celastroides | ʻAkoko | Indigenous | |
| Sesbania tomentosa | ʻOhai | Indigenous | |
| Sida fallax | ʻIlima | Indigenous | |
| Boerhavia repens | Alena | Indigenous | |
| Rumex albescens | Huʻahuʻakō | Indigenous | |
| Portulaca lutea | ʻIhi | Indigenous | |
| Portulaca oleracea | Common purslane | Naturalized alien | |
| Portulaca villosa | Hairy purslane, ʻIhi | Indigenous | |
| Solanum americanum | Popolo | Indigenous | |
| Solanum nelsonii | Indigenous | ||
| Tribulus cistoides | Nohu | Indigenous |