Philip Birnbaum also Paltiel Birnbaum (Kielce, 1904–1988) was an American religious author and translator, best known for his translation and annotation of the siddur (Jewish Prayer Book), first published in 1949.
Birnbaum was born in Kielce, Poland and emigrated to the United States in 1923. He attended Howard College and received his Ph.D. from Dropsie College. He served for several years as the principal of a Jewish day school in Wilmington, Delaware, and directed Jewish schools in Birmingham, Alabama, and Camden, New Jersey. He was a regular columnist and book reviewer for the Hebrew-language weekly, Hadoar. He also served on the board of directors of the Histadrut Ivrit b'America, an American association for the promotion of Hebrew language and culture. 
His works include translations (with annotation and introductory material) of the Siddur, the Machzor, the Torah with Haftorot, and the Passover Haggadah. These translations sought to express reverence without appearing archaic. His Siddur and Machzor were pioneering in that the Hebrew text is of uniform typeface, "unlike the helter-skelter boldface paragraphing... found in Old World siddurim".  His siddur also contains the rarely published Megillat Antiochus. Until the recent advent of the Artscroll translations, "the Birnbaum" Siddur and Machzor were widely used in Orthodox (and Conservative) synagogues, selling over 300,000 copies. These works presented "an accessible American English translation" and were pioneering in addressing American Jews' "perceived deficiencies in personal and communal prayer". 
Birnbaum is also well known for his works of popular Judaism: his excerpted translation of Maimonides Mishne Torah, was one of the first into English; his "Encyclopedia of Jewish Concepts" and "A Treasury of Judaism" (an Anthology excerpting over 70 classic works) were widely referenced. He also produced a "readable" summary and translation of the Tanach.
On his death, one writer described him as "the most obscure best-selling author". It is noteworthy that an immigrant at age 19 should achieve such status as a translator into English.
- Daily Prayer Book: Ha-Siddur Ha-Shalem. Hebrew Publishing Company, 1977. ISBN 0884820548
- High Holyday Prayer Book. Hebrew Publishing Company, 1979. ISBN 0884822400
- Prayer Book for Sabbath and Festivals. Hebrew Publishing Company, 1977. ISBN 0884820548
- The Birnbaum Haggadah. Hebrew Publishing Company, 1976. ISBN 0884829081
- The Concise Jewish Bible. Hebrew Publishing Company, 1977. ISBN 0884824519
- Torah and the Haftarot. Hebrew Publishing Company, 1983. ISBN 0884844560
- Maimonides Mishneh Torah (Yad Hazakah). Hebrew Publishing Company, 1970. ISBN 0884824365
- Encyclopedia of Jewish Concepts. Hebrew Publishing Company, 1979. ISBN 0884829308
- Pereira, Shlomo (2003-05-26). "Hadrat Melech: biographical notes".
- "Jewish Virtual LIbrary: BIRNBAUM, PHILIP".
- Guide to the Records of Histadruth Ivrith of America, jewishideasdaily.com
- Jager, Elliot (2007-04-17). "Power and Politics: Prayer books and resurrection".
- Berman, Saul (2009-08-19). "Even a New Siddur Can’t Close ‘God Gap’". The Forward.
- Goldman, Ari L. (1988-03-22). "Philip Birnbaum, 83, Author of Books For Jewish Liturgy". The New York Times.