Karl M Baer
- Category : 1885-births
- Type : GP
- Profile : 6/2 - Role Model / Hermit
- Definition : Single
- Incarnation Cross : LAX Uncertainty 1
German-Israeli intersex author, social worker, reformer, suffragist and Zionist. Assigned female at birth and named Martha Baer, he became, in December 1906, one of the first people to undergo sex-change surgery, and one of the first, in January 1907, to gain full legal recognition of his gender identity and to have a new birth certificate issued reflecting his new gender. Baer wrote notes for sexologist Magnus Hirschfeld on his experiences growing up as a girl while feeling inside that he was male. Together they developed these notes into the semi-fictional, semi-autobiographical Aus eines Mannes Mädchenjahren (Memoirs of a Man's Maiden Years) (1907) which was published under the pseudonym N.O. Body. Baer also gained the right to marry and did so in October 1907. He died in Tel Aviv on 26 June 1956, aged 71.