1. Ibaliidae Thomson 1862
2. Iblidae Leach 1825
3. Ichneumonidae Latreille 1802
4. Ichthyophthiriidae Kent 1881
5. Ictaluridae T.N. Gill 1861
6. Idioiblidae Buckeridge & Newman 2006
7. Idoteidae Samouelle 1819
8. Iguanidae Oppel 1811
9. Illiciaceae A.C. Smith 1947
10. Iphionidae Kinberg 1856
11. Ischnochitonidae Dall 1889
12. Ischyroceridae Stebbing 1899
13. Isonidae Rosen 1964
14. Isonychiidae Burks 1953
15. Isoparorchiidae Poche 1926
16. Istiophoridae Rafinesque 1810
17. Ixodidae C.L. Koch 1844