The Tree of Europe · Person

William I of Bavaria-Straubing

Duke of Bavaria-Straubing and Count of Hainaut, Holland and Zeeland through his mother’s inheritance. His mental illness led his brother Albert to govern as regent from 1358.

1330 – 1389DukeWittelsbach · ES

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This complete profile is available in English. Bibliographic titles retain their original language. Links marked ES open the Spanish edition.

Historical profile

Key details

Birth: 1330 Pending review

Death: 1389 Pending review

Role: Duke

Dynasty: Wittelsbach · ES

Territories: Bavaria (ES) · Holland (ES) · Hainaut (ES) · Zeeland (ES)

Recorded governments and reigns

Duke · Bavaria · Duchy Inferred1347–1358Branch rule

Duke · Bavaria · Duchy Inferred1359–1389Titular

Count · Holland · County Pending review1354–1358Effective rule

Count · Holland · County Pending review1358–1389TitularHe retained the title during his brother Albert’s government.

Count · Hainaut · County Pending review1356–1358Effective rule

Count · Hainaut · County Pending review1358–1389TitularHe retained the title during his brother Albert’s government.

Count · Zeeland · County Pending review1354–1358Effective rule

Count · Zeeland · County Pending review1358–1389TitularHe retained the title during his brother Albert’s government.

Family network

Recorded relationships

Parents

Louis IV of BavariaPending reviewMargaret II of Hainaut · ESPending review

Partners

Matilda of Lancaster · ESPending review

Crowns and unions

Their titles over time

Follow the changing territories and offices of William I of Bavaria-Straubing. Each title retains its own status.

Period

Governments in 1356

BavariaDuke
View titles and jurisdictions
- Bavaria · ESDuke · Branch rule · William I of Bavaria-Straubing1347–1358
HollandCount
View titles and jurisdictions
- Holland · ESCount · Effective rule1354–1358
HainautCount
View titles and jurisdictions
- Hainaut · ESCount · Effective rule1356–1358
ZeelandCount
View titles and jurisdictions
- Zeeland · ESCount · Effective rule1354–1358

Annual dates: overlap within one year does not prove that two offices were held on the same day. Regencies and co-rulerships retain their labels.

How these titles came together

1354 · HollandAgreement
After the conflict between Margaret and her son, the agreement of 1354 assigned Holland and Zeeland to William. Hainaut remained with Margaret until 1356.
Reference Reference
1356 · HainautInheritance
William inherited Hainaut on his mother’s death. He had already ruled Holland and Zeeland since the agreement of 1354: succession occurred at different dates in the three counties.
Reference Reference

Selected explained accessions. Other titles remain in the profile’s list of recorded governments.

Evidence for this profile

15 recorded claims · 13 without a claim-specific source. Context references do not by themselves verify every fact.

Dates (0/2 with a precise source)

BirthPending review
1330
A precise source has not yet been added.
No individual review recorded ·
DeathPending review
1389
A precise source has not yet been added.
No individual review recorded ·

Family and relationships (0/3 with a precise source)

FatherPending review
Louis IV of Bavaria
A precise source has not yet been added.
No individual review recorded ·
MotherPending review
Margaret II of Hainaut
A precise source has not yet been added.
No individual review recorded ·
Marriage or partnershipPending review
Matilda of Lancaster
A precise source has not yet been added.
No individual review recorded ·

Governments (2/8 with a precise source)

GovernmentInferred
Duke · Bavaria · 1347–1358
To be completed with the existing biographical evidence of his incapacity and Albert’s regency; William is not represented as the effective authority in the core territory after 1358.
Historisches Lexikon Bayerns · Gerhard Immler · Partitions of 1255, 1349, 1353 and 1392; towns of each branch; division of Straubing in 1429; Ingolstadt inheritance in 1445 and agreement of 1450; cessions of 1505.
Reviewed on 2026-10-07 by El Árbol de Europa ·
GovernmentInferred
Duke · Bavaria · 1359–1389
To be completed with the existing biographical evidence of his incapacity and Albert’s regency; William is not represented as the effective authority in the core territory after 1358.
Historisches Lexikon Bayerns · Gerhard Immler · Partitions of 1255, 1349, 1353 and 1392; towns of each branch; division of Straubing in 1429; Ingolstadt inheritance in 1445 and agreement of 1450; cessions of 1505.
Reviewed on 2026-10-07 by El Árbol de Europa ·
GovernmentPending review
Count · Holland · 1354–1358
A precise source has not yet been added.
No individual review recorded ·
GovernmentPending review
Count · Holland · 1358–1389
A precise source has not yet been added.
No individual review recorded ·
GovernmentPending review
Count · Hainaut · 1356–1358
A precise source has not yet been added.
No individual review recorded ·
GovernmentPending review
Count · Hainaut · 1358–1389
A precise source has not yet been added.
No individual review recorded ·
GovernmentPending review
Count · Zeeland · 1354–1358
A precise source has not yet been added.
No individual review recorded ·
GovernmentPending review
Count · Zeeland · 1358–1389
A precise source has not yet been added.
No individual review recorded ·

Successions (0/2 with a precise source)

SuccessionPending review
Holland · Margaret II of Hainaut → William I of Bavaria-Straubing · 1354
After the conflict between Margaret and her son, the agreement of 1354 assigned Holland and Zeeland to William. Hainaut remained with Margaret until 1356.A precise source has not yet been added.
No individual review recorded ·
SuccessionPending review
Hainaut · Margaret II of Hainaut → William I of Bavaria-Straubing · 1356
William inherited Hainaut on his mother’s death. He had already ruled Holland and Zeeland since the agreement of 1354: succession occurred at different dates in the three counties.A precise source has not yet been added.
No individual review recorded ·

Editorial history

2026-10-12 · Claim registry added; existing historical data kept. Specific sourcing remains to be reviewed.
2026-10-08 · Claim registry added; existing historical data kept. Specific sourcing remains to be reviewed.
2026-10-04 · Claim registry added; existing historical data kept. Specific sourcing remains to be reviewed.
2026-10-04 · Claim registry added; existing historical data kept. Specific sourcing remains to be reviewed.
2026-10-03 · Claim registry added; existing historical data kept. Specific sourcing remains to be reviewed.
2026-09-30 · The duchy is limited to Dijon and Autun; each other fief now enters the map only under its dated ruler. John III of Namur and the Nevers/Rethel branch were added. The previous shape combined later counties and unrelated lands as if all belonged to the duchy from 1363.
2026-09-28 · Claim registry added; existing historical data kept. Specific sourcing remains to be reviewed.

Keep exploring

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