This is a list of states in the Holy Roman Empire beginning with the letter I:
| Name | Type | Imperial circle | Imperial diet | History |
|---|---|---|---|---|
 Inner Austria | Duchy | 1379: Partitioned from Austria 1406: Annexed to Austria | ||
 Irsee | Abbacy | Swab | SP | 1186: Formed 1695: Imperial immediacy 1802: To Bavaria |
 Isenberg-Limburg | County | n/a | n/a | 1253: Renamed from Altena-Isenberg 1289: Acquired Altenhof and Styrum 1304: Partitioned into Limburg-Hohenlimburg and Limburg-Styrum |
 Isenburg HRE Prince of Isenburg | Lordship | n/a | n/a | 11th Century: Counts of the Niederlahngau assumed the name Isenburg though without comital rank 1129: Acquired Kobern 1137: Partitioned into Isenburg-Kobern and Isenburg-Isenburg 1197: Rembold IV acquired Kempenich, founding Isenburg-Kempenich c1100: Division into Isenburg-Limburg and Isenburg-Kempenich 1137: Partitioned into Isenburg-Isenburg and Isenburg-Limburg-Covern 1673: Division into Isenburg, Birstein, Isenburg-Marienborn, Isenburg-Meerholz, Isenburg-Wachtersbach 1806: Joined Confederation of the Rhine |
| Isenburg-Arenfels | Lordship | n/a | n/a | c. 1280: Partitioned from Isenburg-Cleeberg 1371: Extinct; to Isenburg-Isenburg |
| Isenburg-Birstein | County 1744: Principality | Upp Rhen | WT | 1511: Partitioned from Isenburg-Büdingen 1628: Partitioned into Isenburg-Offenbach and Isenburg-Büdingen 1685: Partitioned from Isenburg-Offenbach 1744: HRE Prince 1803: Bench of Princes 1806: Renamed to Principality of Isenburg and mediatised the other branches of the House of Isenburg 1815: To the Grand Duchy of Hesse; renamed to Ysenburg and Büdingen |
 Isenburg-Braunsberg | Lordship | n/a | n/a | c. 1175: Partitioned from Isenburg-Isenburg 1243: Renamed to Isenburg-Wied after inheriting Wied |
| Isenburg-Büdingen | Lordship 1442: County | n/a | n/a | 1341: Partitioned from Isenburg-Cleeberg 1442: HRE Count 1511: Partitioned into Isenburg-Rönneburg and Isenburg-Birstein 1628: Partitioned from Isenburg-Birstein 1673: Partitioned into itself, Isenburg-Wächtersbach, Isenburg-Meerholz and Isenburg-Marienborn 1806: To Isenburg-Birstein 1815: To the Grand Duchy of Hesse |
| Isenburg-Cleeberg (Isenburg-Cleberg) | Lordship | n/a | n/a | c. 1158: Partitioned from Isenburg-Kobern 1221: Acquired Limburg an der Lahn 1258: Partitioned into itself and Isenburg-Limburg c. 1280: Partitioned into Isenburg-Arenfels and itself 1304: Acquired Büdingen 1310: Acquired Grenzau 1341: Partitioned into Isenburg-Büdingen and Isenburg-Grenzau |
| Isenburg-Eisenberg | County | n/a | n/a | 1685: Partitioned from Isenburg-Offenbach 1758: Extinct; to Isenburg-Birstein |
| Isenburg-Grenzau | Lordship | n/a | n/a | 1341: Partitioned from Isenburg-Cleeberg 1439: Extinct; to Nassau-Beilstein 1446: To the Archbishopric of Trier 1460: To Isenburg-Isenburg (Lower Isenburg) |
 Isenburg-Grenzau | Lordship | n/a | n/a | 1502: Partitioned from Isenburg-Isenburg (Lower Isenburg) 1664: Extinct; divided between the Archbishoprics of Cologne and Trier and Fulda Abbey, with the latter granting their share of the territory to Walderdorff |
| Isenburg-Isenburg (Lower Isenburg) | Lordship | n/a | n/a | 1137: Partitioned from Isenburg c. 1175: Partitioned into itself and Isenburg-Braunsberg 1197: Acquired Kempenich c. 1220: Partitioned into itself and Isenburg-Kempenich 1460: Acquired Grenzau 1497: Acquired Neumagen 1502: Partitioned into Isenburg-Grenzau and Isenburg-Neumagen |
| Isenburg-Kempenich | Lordship | n/a | n/a | 1277: Made fief of the Archbishopric of Trier 1424: Extinct; to Schöneck |
| Isenburg-Kobern (Isenburg-Covern) | Lordship | n/a | n/a | 1137: Partitioned from Isenburg c. 1158: Partitioned into itself and Isenburg-Cleeberg 1195: Made fief of the Archbishopric of Trier 1266: Extinct; to Neuerburg |
| Isenburg-Limburg | Lordship | n/a | n/a | 1258: Partitioned from Isenburg-Cleeberg 1406: Extinct; to the Archbishopric of Trier |
| Isenburg-Marienborn | Lordship 1442: County | Upp Rhen | n/a | 1673: Partitioned from Isenburg-Büdingen 1725: Extinct; divided between Isenburg-Büdingen, Isenburg-Wächtersbach and Isenburg-Meerholz |
| Isenburg-Meerholz | Lordship 1442: County | Upp Rhen | n/a | 1673: Partitioned from Isenburg-Büdingen 1806: To Isenburg-Birstein 1815: To the Grand Duchy of Hesse |
| Isenburg-Neumagen | Lordship | n/a | n/a | 1502: Partitioned from Isenburg-Isenburg (Lower Isenburg) 1554: Extinct; to Sayn-Wittgenstein |
| Isenburg-Offenbach | County | Upp Rhen | n/a | 1628: Partitioned from Isenburg-Birstein 1685: Partitioned into Isenburg-Philippseich, Isenburg-Birstein and Isenburg-Eisenberg |
| Isenburg-Philippseich | County | Upp Rhen | n/a | 1685: Partitioned from Isenburg-Offenbach 1718: Extinct; given as an appanage to his nephew William Maurice II, Count of Isenburg-Philippseich without imperial immediacy nor representation in the imperial diet |
| Isenburg-Rönneburg | County | Upp Rhen | n/a | 1511: Partitioned from Isenburg-Büdingen 1601: Extinct; to Isenburg-Birstein |
| Isenburg-Wächtersbach | Lordship 1442: County | Upp Rhen | n/a | 1673: Partitioned from Isenburg-Büdingen 1806: To Isenburg-Birstein 1815: To the Grand Duchy of Hesse |
| Isenburg-Wied | County | n/a | n/a | 1243: Renamed from Isenburg-Braunsberg after inheriting Wied 1462: Extinct; to Runkel |
 Isny im Allgäu | Imperial City | Swab | SW | 1365: Free Imperial City 1803: To Quadt 1806: To Württemberg |
 Istria | Margraviate | n/a | n/a | 1040: Given to Poppo of Weimar-Orlamünde, also of Carniola 1173: To Andechs-Meran 1209: To the Patriarchate of Aquileia 13th Century: Most to Venice 1374: To Austria as mediate province through Carniola 1420: Rest of Istria to Venice 1797: Venetian parts to Austria 1805: To Italy 1815: To Austria |
 Itter | Lordship |
