diff --git a/adminSiteClient/EditorCustomizeTab.tsx b/adminSiteClient/EditorCustomizeTab.tsx
index cdbc1cb260..ae3cdf5bed 100644
--- a/adminSiteClient/EditorCustomizeTab.tsx
+++ b/adminSiteClient/EditorCustomizeTab.tsx
@@ -577,9 +577,9 @@ export class EditorCustomizeTab<
                                         }
                                         resetButton={{
                                             onClick: () =>
-                                                (yAxisConfig.min = undefined),
+                                                (yAxisConfig.min = Infinity),
                                             disabled:
-                                                yAxisConfig.min === undefined,
+                                                yAxisConfig.min === Infinity,
                                         }}
                                         allowDecimal
                                         allowNegative
@@ -592,9 +592,9 @@ export class EditorCustomizeTab<
                                         }
                                         resetButton={{
                                             onClick: () =>
-                                                (yAxisConfig.max = undefined),
+                                                (yAxisConfig.max = -Infinity),
                                             disabled:
-                                                yAxisConfig.max === undefined,
+                                                yAxisConfig.max === -Infinity,
                                         }}
                                         allowDecimal
                                         allowNegative
diff --git a/db/migration/1729763649580-SetYAxisMinDefaultToZero.ts b/db/migration/1729763649580-SetYAxisMinDefaultToZero.ts
new file mode 100644
index 0000000000..6da7e2d2c1
--- /dev/null
+++ b/db/migration/1729763649580-SetYAxisMinDefaultToZero.ts
@@ -0,0 +1,123 @@
+import { defaultGrapherConfig } from "@ourworldindata/grapher"
+import { mergeGrapherConfigs } from "@ourworldindata/utils"
+import { MigrationInterface, QueryRunner } from "typeorm"
+
+export class SetYAxisMinDefaultToZero1729763649580
+    implements MigrationInterface
+{
+    public async up(queryRunner: QueryRunner): Promise<void> {
+        // when inheritance is disabled, set yAxis.min explicitly to "auto"
+        // for charts that used to rely on "auto" being the default
+        await queryRunner.query(`
+             -- sql
+             UPDATE chart_configs cc
+             JOIN charts c ON cc.id = c.configId
+             SET
+                 cc.patch = JSON_SET(cc.patch, '$.yAxis.min', 'auto'),
+                 cc.full = JSON_SET(cc.full, '$.yAxis.min', 'auto')
+             WHERE
+                 cc.full ->> '$.type' = 'LineChart'
+                 AND cc.patch ->> '$.yAxis.min' IS NULL
+                 AND c.isInheritanceEnabled IS FALSE
+         `)
+
+        // set yAxis.min to "auto" for etl-authored configs for configs
+        // that used to rely on "auto" being the default
+        await queryRunner.query(`
+             -- sql
+             UPDATE chart_configs cc
+             JOIN variables v ON cc.id = v.grapherConfigIdETL
+             SET
+                 cc.patch = JSON_SET(cc.patch, '$.yAxis.min', 'auto'),
+                 cc.full = JSON_SET(cc.full, '$.yAxis.min', 'auto')
+             WHERE
+                COALESCE(cc.patch ->> '$.type', 'LineChart') = 'LineChart'
+                AND cc.patch ->> '$.yAxis.min' IS NULL
+         `)
+
+        // update admin-authored configs (we don't currently have any in use
+        // but included for completeness)
+        const indicatorConfigs = await queryRunner.query(`
+             -- sql
+             SELECT
+                 v.id AS variableId,
+                 cc_admin.id AS adminConfigId,
+                 cc_admin.patch AS adminConfig,
+                 cc_etl.patch AS etlConfig
+             FROM variables v
+             JOIN chart_configs cc_admin ON cc_admin.id = v.grapherConfigIdAdmin
+             JOIN chart_configs cc_etl ON cc_etl.id = v.grapherConfigIdETL
+             WHERE
+                COALESCE(cc_etl.patch ->> '$.type', 'LineChart') = 'LineChart'
+                AND cc_etl.patch ->> '$.yAxis.min' = 'auto'
+         `)
+
+        for (const indicator of indicatorConfigs) {
+            const fullConfig = mergeGrapherConfigs(
+                indicator.etlConfig ?? {},
+                indicator.adminConfig ?? {}
+            )
+
+            await queryRunner.query(
+                `
+                    -- sql
+                    UPDATE chart_configs cc
+                    SET cc.full = ?
+                    WHERE cc.id = ?
+                `,
+                [JSON.stringify(fullConfig), indicator.adminConfigId]
+            )
+        }
+
+        // Update the full configs of all charts that inherit from an indicator
+        const charts = await queryRunner.query(`
+             -- sql
+             SELECT
+                 cc.id AS configId,
+                 cc.patch AS patchConfig,
+                 cc_etl.patch AS etlConfig,
+                 cc_admin.patch AS adminConfig
+             FROM charts c
+             JOIN chart_configs cc ON cc.id = c.configId
+             JOIN charts_x_parents p ON p.chartId = c.id
+             JOIN variables v ON v.id = p.variableId
+             LEFT JOIN chart_configs cc_etl ON cc_etl.id = v.grapherConfigIdETL
+             LEFT JOIN chart_configs cc_admin ON cc_admin.id = v.grapherConfigIdAdmin
+             WHERE c.isInheritanceEnabled IS TRUE
+         `)
+
+        for (const chart of charts) {
+            // if neither the indicator chart nor the patch config specified a yAxis
+            // min value, then the chart used to rely on the default "auto" value
+            if (
+                chart.etlConfig.yAxis.min === undefined &&
+                chart.patchConfig.yAxis.min === undefined
+            ) {
+                chart.patchConfig.yAxis.min = "auto"
+            }
+
+            const fullConfig = mergeGrapherConfigs(
+                defaultGrapherConfig,
+                chart.etlConfig ?? {},
+                chart.adminConfig ?? {},
+                chart.patchConfig
+            )
+
+            await queryRunner.query(
+                `
+                    -- sql
+                    UPDATE chart_configs cc
+                    SET cc.full = ?
+                    WHERE cc.id = ?
+                `,
+                [JSON.stringify(fullConfig), chart.configId]
+            )
+        }
+    }
+
+    public async down(): Promise<void> {
+        throw new Error(
+            "Migration SetYAxisMinDefaultToZero1729763649580 can't be reverted"
+        )
+    }
+}
diff --git a/packages/@ourworldindata/grapher/src/axis/AxisConfig.ts b/packages/@ourworldindata/grapher/src/axis/AxisConfig.ts
index 2226665d24..676da96add 100644
--- a/packages/@ourworldindata/grapher/src/axis/AxisConfig.ts
+++ b/packages/@ourworldindata/grapher/src/axis/AxisConfig.ts
@@ -45,10 +45,17 @@ class AxisConfigDefaults implements AxisConfigInterface {
     @observable.ref domainValues?: number[] = undefined
 }
 
-function parseAutoOrNumberFromJSON(
+function parseMinFromJSON(
     value: AxisMinMaxValueStr.auto | number | undefined
 ): number | undefined {
-    if (value === AxisMinMaxValueStr.auto) return undefined
+    if (value === AxisMinMaxValueStr.auto) return Infinity
+    return value
+}
+
+function parseMaxFromJSON(
+    value: AxisMinMaxValueStr.auto | number | undefined
+): number | undefined {
+    if (value === AxisMinMaxValueStr.auto) return -Infinity
     return value
 }
 
@@ -67,8 +74,8 @@ export class AxisConfig
     // todo: test/refactor
     updateFromObject(props?: AxisConfigInterface): void {
         if (props) extend(this, props)
-        if (props?.min) this.min = parseAutoOrNumberFromJSON(props?.min)
-        if (props?.max) this.max = parseAutoOrNumberFromJSON(props?.max)
+        if (props?.min) this.min = parseMinFromJSON(props?.min)
+        if (props?.max) this.max = parseMaxFromJSON(props?.max)
     }
 
     toObject(): AxisConfigInterface {
@@ -96,8 +103,8 @@ export class AxisConfig
 
         deleteRuntimeAndUnchangedProps(obj, new AxisConfigDefaults())
 
-        if (obj.min === undefined) obj.min = AxisMinMaxValueStr.auto
-        if (obj.max === undefined) obj.max = AxisMinMaxValueStr.auto
+        if (obj.min === Infinity) obj.min = AxisMinMaxValueStr.auto
+        if (obj.max === -Infinity) obj.max = AxisMinMaxValueStr.auto
 
         return obj
     }
diff --git a/packages/@ourworldindata/grapher/src/lineCharts/LineChart.tsx b/packages/@ourworldindata/grapher/src/lineCharts/LineChart.tsx
index 6b6e2b64ce..37d5c4f16e 100644
--- a/packages/@ourworldindata/grapher/src/lineCharts/LineChart.tsx
+++ b/packages/@ourworldindata/grapher/src/lineCharts/LineChart.tsx
@@ -1342,6 +1342,8 @@ export class LineChart
                 // horizontal axis to be at the bottom of the chart.
                 // see https://github.com/owid/owid-grapher/pull/975#issuecomment-890798547
                 singleValueAxisPointAlign: AxisAlign.start,
+                // default to 0 if not set
+                min: 0,
                 ...this.manager.yAxisConfig,
             },
             this
diff --git a/packages/@ourworldindata/grapher/src/schema/defaultGrapherConfig.ts b/packages/@ourworldindata/grapher/src/schema/defaultGrapherConfig.ts
index 6497d08f13..dd0f68334e 100644
--- a/packages/@ourworldindata/grapher/src/schema/defaultGrapherConfig.ts
+++ b/packages/@ourworldindata/grapher/src/schema/defaultGrapherConfig.ts
@@ -26,7 +26,6 @@ export const defaultGrapherConfig = {
     maxTime: "latest",
     yAxis: {
         removePointsOutsideDomain: false,
-        min: "auto",
         scaleType: "linear",
         max: "auto",
         canChangeScaleType: false,
@@ -66,7 +65,6 @@ export const defaultGrapherConfig = {
     },
     xAxis: {
         removePointsOutsideDomain: false,
-        min: "auto",
         scaleType: "linear",
         max: "auto",
         canChangeScaleType: false,
diff --git a/packages/@ourworldindata/grapher/src/schema/grapher-schema.005.yaml b/packages/@ourworldindata/grapher/src/schema/grapher-schema.005.yaml
index 79ca82b412..4465a68f6c 100644
--- a/packages/@ourworldindata/grapher/src/schema/grapher-schema.005.yaml
+++ b/packages/@ourworldindata/grapher/src/schema/grapher-schema.005.yaml
@@ -514,8 +514,9 @@ $defs:
                 type: string
                 description: Axis label
             min:
-                description: Minimum domain value of the axis. Inferred from data if set to "auto".
-                default: auto
+                description: |
+                    Minimum domain value of the axis. Inferred from data if set to "auto".
+                    Usually defaults to "auto", but defaults to 0 for line charts on the y-axis.
                 oneOf:
                     - type: number
                     - type: string