|Location||Hytekia, Juznia, Lilienburg, Mascylla|
|Primary inflows||Lanne River, Wehle River, Adel River|
|Primary outflows||Blaugold River, Mögde River|
|Catchment area||128,000 km2 (49,300 sq mi)|
|Basin countries||Hytekia, Juznia, Krumlau, Lilienburg, Mascylla|
|Max. length||408 km (253.5 mi)|
|Max. width||118 km (73.3 mi)|
|Surface area||32,324 km2 (12,480 sq mi)|
|Average depth||112 m (367 ft)|
|Max. depth||567 m (1,860 ft)|
|Water volume||X km3 (X cu mi)|
|Residence time||8.1 years|
|Shore length1||1,600 km (994 mi)|
|Surface elevation||260 m (853 ft)|
|Frozen||Occasionally in winter|
|1 Shore length is not a well-defined measure.|
Lake Sigismund (Hesurian: Sigismundmeer) is a lake located in the centre of Erdara, south-west of the Weißenhaupt mountains and north of the Central Erdaran Basin, shared between Hytekia and Juznia to the west, Lilienburg to the south-west, and Mascylla to the east. With a size of 32,324 km2 (12,480 sq mi), it is mainland Iraia's largest inland body of water, the largest lake in Erdara and the world's biggest freshwater lake. As an anomaly, the lake has two equal primary outflows to the north as the Blaugold River and Mögde River. It has also one of the largest catchment areas for a lake worldwide, the single largest in Erdara, and its shores are globally the most populated with around 11 million inhabitants.
Its creation can be attributed to the last major ice age, as glaciers carved out the basin to form the depression that would later be filled by the melt water of the ice cap as it melted away around 11,500 years ago. The sea bed in the northern part reaches as low as 567 m (1,860 ft) below sea level, which makes it the third lowest natural depression on Gaia.
Its shorelines are governed by the Mascyllary states of Elpsland, Sigismund, Hohnern and Gothern, the Lilienburger districts of Lilienwald-Sigismundsee, X, the Hytek province of Grobina-Zigmundsesers, and the Juznik X of X. Lake Sigismund is generally regarded as one of the major locations of Erdaran culture, history, religion, and economic development. The lake is tied to an extensive waterway system and thus is the largest transportation hub in Erdara, and a key economic region for the Erdaran Union. Striving for hegemony over the lake has led to multiple conflicts and wars, the most notable of which include the Konreid Campaign, Edelweiss Crisis and Continental War. Maritime borders in the lake have been subject to diplomatic debate and the exploitation of resources an ongoing political, economic, and ecological issue.