The controversial limits of Thlaspi are discussed, and all of its segregates proposed or revised during the past four decades are critically evaluated. As a result, the majority of specific and infraspecific names previously assigned to Thlaspi are currently placed in Noccaea, a genus the limits of which are expanded to include almost all of Thlaspi segregates. A detailed description of Noccaea, a synoptic account of its species, along with full bibliography and typification, and key to all 128 species are presented. The new names N. germanii, N. iranica, and N. meyeri and the following 36 new combinations are proposed: N. abchasica, N. antitaurica, N. atlantica, N. bornmuelleri; N. bovis, N. bulbosa, N. campylophylla, N. cappadocica, N. capricornuta, N. cilicica, N. cornuticarpa, N. crassiuscula, N. dolichocarpa, N. eigii, N. elegans, N. huber-morathii, N. jaubertii, N. kurdica, N. lilacina, N. maassoumii, N. natolica, N. orbiculata, N. oxyceras, N. perfoliata, N. platycarpa, N. pulvinata, N. rechingeri, N. rostrata, N. rosularis, N. stenocarpa, N. szowitsiana, N. triangularis, N. umbellata, N. vesicaria, N. vesicaria subsp. boissieri, and N. zangezurica. The genus Coluteocarpus is reduced to synonymy of Noccaea. Brossardia papyracea var. kotschyi, Coluteocarpus reticulatus var. boissieri, Hutschinsia trinervia, Iberidella andersonii, Thlaspi affine, T. japonicum, T. kovatsii, T. szowitsianum, and Vesicaria reticulata are lectotypified.