person · P0503 · geonim

Shimon Kayyara רב שמעון קיירא

placed by Sefer HaKabbalah in the mid-8th c., before Yehudai Gaon — a dating the geonim's own testimony reverses · 740–850 CE

The author history settled on for the Halachot Gedolot (Halachot Gedolot) — a Babylonian scholar outside the gaonate, remembered from Basra, who built the geonic era's great code out of Halachot Pesukot and the Bavli. Even his century is a machloket: ibn Daud set him before Yehudai Gaon, and the geonim's own testimony sets him two generations after.

Who

Hebrew: רב שמעון קיירא
Also known as: Simeon Kayyara, Shimon Kaira
Era: geonim

When

Traditional: placed by Sefer HaKabbalah in the mid-8th c., before Yehudai Gaon — a dating the geonim's own testimony reverses
Civil (computed): 4500–4610 AM · 740–850 CE
Academic: fl. c. 825–850 CE, Basra
Lifespan (traditional): ≈110 years
Precision: disputed

How do we know

Claim	Evidence	Confidence	Sources
The dominant view, medieval and modern, names Shimon Kayyara as the author of Halachot Gedolot; he held no gaonate and appears in no succession list — a private scholar whose book outranked the office. The authorship edge on Halachot Gedolot is drawn on this attribution, against the minority ascription of the work to Yehudai Gaon found in some rishonim.	tradition reconstruction	★★★☆☆	E. Hildesheimer (ed.), Halachot Gedolot (critical ed. 1971–1987), introduction; R. Brody, The Geonim of Babylonia (1998), ch. on the halachic codes Simeon Kayyara (overview of the attribution debate)
His dating is the classic confusion the audit records: Avraham ibn Daud's Sefer HaKabbalah places him in the mid-8th century, before Yehudai Gaon — which would make Halachot Pesukot the borrower — while the geonim's own testimony and the BeHaG's demonstrable use of Halachot Pesukot reverse the order, dating him c. 825–850. The AM span above covers both positions rather than pretending to a precision the sources lack. Mirrors Halachot Gedolot's dates block (precision: disputed) — person and book are dated by the same contested evidence.	tradition reconstruction	★★★☆☆	Avraham ibn Daud, Sefer HaKabbalah (ed. G. Cohen, 1967); R. Brody, The Geonim of Babylonia (1998) Halachot Gedolot (dating discussion)
His code absorbs Halachot Pesukot (Halachot Pesukot) nearly whole and expands it across the Bavli's practical tractates — the basis of the reception-from-writings edges drawn here: a scholar whose attested teachers are none, and whose attested library is plain on every page.	reconstruction	★★★☆☆	E. Hildesheimer (ed.), Halachot Gedolot, introduction on the sources; R. Brody, The Geonim of Babylonia (1998) Halakhot Gedolot (Sefaria edition)