二碘化钐（化学式：SmI₂），IUPAC名称为碘化钐(II)，绿色固体，用作有机合成中的单电子转移还原剂。对空气敏感，但是反应中可以允许水的存在。一般以0.1mol/L的THF深蓝色溶液的形式出售，钐为七配位，单帽八面体构型。

三碘化钐高温分解、钐粉与1,2-二碘乙烷或二碘甲烷在无水四氢呋喃中反应都可以制得二碘化钐。

二碘化钐可参与的反应有：

随着反应进行，二碘化钐THF溶液的深蓝色逐渐变为淡黄色。反应后的二价钐用稀盐酸处理，以Sm的形式除去。

SmI₂作为碱，可以使甲苯磺酰基可以从N-甲苯磺酰胺中迅速离去。该反应对于合成不稳定的胺更有效，例如氮杂环丙烷：

Samarium(II) iodide (SmI₂, also known as "Kagan's reagent") is a green solid composed of samarium and iodine, with a melting point of 520 °C where the samarium atom has a coordination number of seven in a capped octahedral configuration. It can be formed by high temperature decomposition of samarium(III) iodide (SmI₃), the more stable iodide. A convenient lab preparation is to react Sm powder with diiodoethane (ICH₂CH₂I) in anhydrous THF, or diiodomethane (CH₂I₂) may also be used. Samarium(II) iodide is a powerful reducing agent – for example it rapidly reduces water to hydrogen. It is available commercially as a dark blue 0.1 M solution in THF.