diff --git a/src/lib/types/api/characterSeries.ts b/src/lib/types/api/characterSeries.ts
new file mode 100644
index 00000000..41210fa0
--- /dev/null
+++ b/src/lib/types/api/characterSeries.ts
@@ -0,0 +1,88 @@
+/**
+ * Character Series Types
+ *
+ * Type definitions for character series data from the API.
+ * CharacterSeries is a database-driven classification system for characters.
+ * Unlike weapons (one-to-many), characters can belong to multiple series (many-to-many).
+ *
+ * @module types/api/characterSeries
+ */
+
+/**
+ * Embedded series reference on characters.
+ * This is the structure returned in character.series field (array).
+ */
+export interface CharacterSeriesRef {
+	id: string
+	slug: string
+	name: { en: string; ja: string }
+}
+
+/**
+ * Full character series from /api/v1/character_series endpoint.
+ * characterCount is only included in the :full view (show endpoint).
+ */
+export interface CharacterSeries {
+	id: string
+	name: { en: string; ja: string }
+	slug: string
+	order: number
+	characterCount?: number
+}
+
+/**
+ * Input type for character series form (client-side)
+ */
+export interface CharacterSeriesInput {
+	name_en: string
+	name_jp: string
+	slug: string
+	order: number
+}
+
+/**
+ * Payload for creating a new character series (editor only)
+ */
+export interface CreateCharacterSeriesPayload {
+	name_en: string
+	name_jp: string
+	slug: string
+	order?: number
+}
+
+/**
+ * Payload for updating an existing character series (editor only)
+ */
+export interface UpdateCharacterSeriesPayload {
+	name_en?: string
+	name_jp?: string
+	slug?: string
+	order?: number
+}
+
+/**
+ * Type guard to check if a series value is the new object format vs legacy integer.
+ * During migration, some characters may still have integer series values.
+ *
+ * @param series - The series value to check
+ * @returns True if series is a CharacterSeriesRef object
+ */
+export function isCharacterSeriesRef(series: unknown): series is CharacterSeriesRef {
+	return (
+		series !== null &&
+		typeof series === 'object' &&
+		'slug' in series &&
+		'id' in series &&
+		'name' in series
+	)
+}
+
+/**
+ * Type guard to check if series array contains new object format
+ *
+ * @param series - The series array to check
+ * @returns True if array contains CharacterSeriesRef objects
+ */
+export function hasCharacterSeriesRefs(series: unknown[]): series is CharacterSeriesRef[] {
+	return series.length > 0 && isCharacterSeriesRef(series[0])
+}
diff --git a/src/lib/types/api/summonSeries.ts b/src/lib/types/api/summonSeries.ts
new file mode 100644
index 00000000..bf0a36b0
--- /dev/null
+++ b/src/lib/types/api/summonSeries.ts
@@ -0,0 +1,76 @@
+/**
+ * Summon Series Types
+ *
+ * Type definitions for summon series data from the API.
+ * SummonSeries is a database-driven classification system for summons.
+ *
+ * @module types/api/summonSeries
+ */
+
+/**
+ * Embedded series reference on summons.
+ * This is the structure returned in summon.series field.
+ */
+export interface SummonSeriesRef {
+	id: string
+	slug: string
+	name: { en: string; ja: string }
+}
+
+/**
+ * Full summon series from /api/v1/summon_series endpoint.
+ * summonCount is only included in the :full view (show endpoint).
+ */
+export interface SummonSeries {
+	id: string
+	name: { en: string; ja: string }
+	slug: string
+	order: number
+	summonCount?: number
+}
+
+/**
+ * Input type for summon series form (client-side)
+ */
+export interface SummonSeriesInput {
+	name_en: string
+	name_jp: string
+	slug: string
+	order: number
+}
+
+/**
+ * Payload for creating a new summon series (editor only)
+ */
+export interface CreateSummonSeriesPayload {
+	name_en: string
+	name_jp: string
+	slug: string
+	order?: number
+}
+
+/**
+ * Payload for updating an existing summon series (editor only)
+ */
+export interface UpdateSummonSeriesPayload {
+	name_en?: string
+	name_jp?: string
+	slug?: string
+	order?: number
+}
+
+/**
+ * Type guard to check if a series value is the new object format.
+ *
+ * @param series - The series value to check
+ * @returns True if series is a SummonSeriesRef object
+ */
+export function isSummonSeriesRef(series: unknown): series is SummonSeriesRef {
+	return (
+		series !== null &&
+		typeof series === 'object' &&
+		'slug' in series &&
+		'id' in series &&
+		'name' in series
+	)
+}