• Carex Linnaeus, 1753
• Carex abacta Bailey accepted as Carex michauxiana Boeckl.
• Carex abbreviata Prescott accepted as Carex torreyi Tuckerman
• Carex abdita Bickn. accepted as Carex umbellata Schkuhr ex Willd.
• Carex abitibiana Lepage
• Carex ablata Bailey accepted as Carex luzulina Olney
• Carex aboriginum auct. non M.E. Jones, 1910 accepted as Carex parryana Dewey
• Carex abrupta Mackenzie
• Carex abscondita Mackenzie
• Carex absconditiformis Fern.
• Carex accedens Holm accepted as Carex aperta Boott
• Carex acuta auct. non L. accepted as Carex nigra (L.) Reichard
• Carex acutiformis Ehrh.
• Carex acutinella Mackenzie accepted as Carex aquatilis Wahlenb.
• Carex adelostoma Krecz.
• Carex adusta Boott
• Carex aenea Fern. accepted as Carex foenea Willd.
• Carex aestivaliformis Mackenzie
• Carex aestivalis M.A. Curtis ex Gray
• Carex aggregata Mackenzie
• Carex agrostoides Mackenzie
• Carex alata Torr.
• Carex albicans auct. non Willd. ex Spreng. accepted as Carex peckii Howe
• Carex albicans Willd. ex Spreng.
• Carex albida Bailey
• Carex albolutescens Schwein.
• Carex albonigra Mackenzie
• Carex albursina Sheldon
• Carex allegheniensis Mackenzie accepted as Carex debilis Michx.
• Carex alligata Boott
• Carex alma Bailey
• Carex alopecoidea Tuckerman
• Carex amblyorhyncha Krecz. accepted as Carex marina Dewey
• Carex ambusta Boott accepted as Carex physocarpioides Lepage
• Carex amphibola Steud.
• Carex amphigena (Fern.) Mackenzie accepted as Carex glareosa Schkuhr ex Wahlenb.
• Carex amplectens Mackenzie
• Carex amplifolia Boott
• Carex amplisquama F.J. Herm. accepted as Carex communis Bailey
• Carex anceps Muhl. accepted as Carex laxiflora Lam.
• Carex angarae Steud. accepted as Carex norvegica Retz.
• Carex anguillata Drej.
• Carex angustata Boott
• Carex angustior Mackenzie accepted as Carex echinata Murr.
• Carex annectens (Bickn.) Bickn.
• Carex anthoxanthea J. & K. Presl
• Carex anticostensis (Fern.) Lepage accepted as Carex stenolepis Lessing
• Carex aperta Boott
• Carex apoda Clokey accepted as Carex atrosquama Mackenzie
• Carex appalachica J. Webber & P.W. Ball
• Carex aquatilis Wahlenb.
• Carex arapahoensis Clokey
• Carex arcta Boott
• Carex arctata Boott ex Hook.
• Carex arctiformis Mackenzie
• Carex arctogena H. Sm. accepted as Carex capitata Linnaeus
• Carex arenaria Linnaeus
• Carex arenicola F. Schmidt accepted as Carex pansa Bailey
• Carex argyrantha Tuckerman
• Carex arkansana (Bailey) Bailey
• Carex artitecta Mackenzie accepted as Carex albicans Willd. ex Spreng.
• Carex asa-grayi Bailey accepted as Carex grayi Carey
• Carex assiniboinensis W. Boott
• Carex athabascensis F.J. Herm. accepted as Carex scirpoidea Michx.
• Carex atherodes Spreng.
• Carex athrostachya Olney
• Carex athrostachys Olney
• Carex atlantica Bailey
• Carex atrata auct.p.p. non L. accepted as Carex heteroneura W. Boott
• Carex atrata L.p.p. accepted as Carex atratiformis Britt.
• Carex atratiformis Britt.
• Carex atrofusca Schkuhr
• Carex atrosquama Mackenzie
• Carex aurea Nutt.
• Carex austrina Mackenzie
• Carex austrocaroliniana Bailey
• Carex backii Boott
• Carex baileyi Britt.
• Carex baltzellii Chapman ex Dewey
• Carex barbarae Dewey
• Carex barrattii Schwein. & Torr.
• Carex basiantha Steud.
• Carex bayardii Fern. accepted as Carex crus-corvi Shuttlw. ex Kunze
• Carex bebbii Olney ex Fern.
• Carex behringensis C.B. Clarke accepted as Carex podocarpa R. Br.
• Carex bella Bailey
• Carex bicknellii Britt.
• Carex bicolor Bellardi ex All.
• Carex bifida W. Boott accepted as Carex serratodens W. Boott
• Carex bigelowii Torr. ex Schwein.
• Carex biltmoreana Mackenzie
• Carex bipartita All. accepted as Carex lachenalii Schkuhr
• Carex blanda Dewey
• Carex boecheriana A. & D. Love & Raymond
• Carex bolanderi Olney
• Carex bonanzensis Britt.
• Carex bonplandii Kunth
• Carex brachyglossa Mackenzie accepted as Carex annectens (Bickn.) Bickn.
• Carex brainerdii Mackenzie
• Carex brevicaulis Mackenzie