diff --git a/adminSiteClient/EditorCustomizeTab.tsx b/adminSiteClient/EditorCustomizeTab.tsx
index cdbc1cb260b..ae3cdf5bedc 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 00000000000..cdf196aacb9
--- /dev/null
+++ b/db/migration/1729763649580-SetYAxisMinDefaultToZero.ts
@@ -0,0 +1,177 @@
+import { mergeGrapherConfigs } from "@ourworldindata/utils"
+import { MigrationInterface, QueryRunner } from "typeorm"
+
+export class SetYAxisMinDefaultToZero1729763649580
+    implements MigrationInterface
+{
+    public async up(queryRunner: QueryRunner): Promise<void> {
+        // charts with inheritance disabled:
+        // set yAxis.min explicitly to "auto" for line 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
+                -- using JSON_MERGE_PATCH instead of JSON_SET in case yAxis doesn't exist
+                cc.patch = JSON_MERGE_PATCH(cc.patch, '{"yAxis":{"min":"auto"}}')
+            WHERE
+                cc.full ->> '$.type' = 'LineChart'
+                AND c.isInheritanceEnabled IS FALSE
+                AND cc.patch ->> '$.yAxis.min' IS NULL
+        `)
+
+        // charts with inheritance enabled:
+        // set yAxis.min explicitly to "auto" for line charts
+        // that used to rely on "auto" being the default.
+        // this is the case for charts where neither the patch config
+        // of the chart itself nor the indicator config have yAxis.min set
+        await queryRunner.query(`
+            -- sql
+            UPDATE chart_configs cc
+            JOIN charts c ON cc.id = c.configId
+            -- keep charts without parent indicator
+            LEFT JOIN charts_x_parents cxp ON cxp.chartId = c.id
+            LEFT JOIN variables v ON v.id = cxp.variableId
+            LEFT JOIN chart_configs cc_admin ON cc_admin.id = v.grapherConfigIdAdmin
+            SET
+                -- using JSON_MERGE_PATCH instead of JSON_SET in case yAxis doesn't exist
+                cc.patch = JSON_MERGE_PATCH(cc.patch, '{"yAxis":{"min":"auto"}}')
+            WHERE
+                cc.full ->> '$.type' = 'LineChart'
+                AND c.isInheritanceEnabled IS TRUE
+                AND cc.patch ->> '$.yAxis.min' IS NULL
+                AND (
+                    cc_admin.full IS NULL
+                    OR cc_admin.full ->> '$.yAxis.min' IS NULL
+                )
+        `)
+
+        // recompute all full configs (we need to update all charts
+        // since the defaultGrapherConfig has changed)
+        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,
+                 c.isInheritanceEnabled
+             FROM charts c
+             JOIN chart_configs cc ON cc.id = c.configId
+             LEFT JOIN charts_x_parents cxp ON cxp.chartId = c.id
+             LEFT JOIN variables v ON v.id = cxp.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
+         `)
+        for (const chart of charts) {
+            const patchConfig = JSON.parse(chart.patchConfig)
+
+            const etlConfig = chart.etlConfig
+                ? JSON.parse(chart.etlConfig)
+                : undefined
+            const adminConfig = chart.adminConfig
+                ? JSON.parse(chart.adminConfig)
+                : undefined
+
+            const fullConfig = mergeGrapherConfigs(
+                defaultGrapherConfig as any,
+                chart.isInheritanceEnabled ? etlConfig ?? {} : {},
+                chart.isInheritanceEnabled ? adminConfig ?? {} : {},
+                patchConfig
+            )
+
+            await queryRunner.query(
+                `
+                    -- sql
+                    UPDATE chart_configs cc
+                    SET cc.full = ?
+                    WHERE cc.id = ?
+                `,
+                [JSON.stringify(fullConfig), chart.configId]
+            )
+        }
+    }
+
+    // eslint-disable-next-line @typescript-eslint/no-empty-function
+    public async down(): Promise<void> {}
+}
+
+const defaultGrapherConfig = {
+    $schema: "https://files.ourworldindata.org/schemas/grapher-schema.005.json",
+    map: {
+        projection: "World",
+        hideTimeline: false,
+        colorScale: {
+            equalSizeBins: true,
+            binningStrategy: "ckmeans",
+            customNumericColorsActive: false,
+            colorSchemeInvert: false,
+            binningStrategyBinCount: 5,
+        },
+        toleranceStrategy: "closest",
+        tooltipUseCustomLabels: false,
+        time: "latest",
+    },
+    maxTime: "latest",
+    yAxis: {
+        removePointsOutsideDomain: false,
+        min: "auto",
+        scaleType: "linear",
+        max: "auto",
+        canChangeScaleType: false,
+        facetDomain: "shared",
+    },
+    tab: "chart",
+    matchingEntitiesOnly: false,
+    hasChartTab: true,
+    hideLegend: false,
+    hideLogo: false,
+    timelineMinTime: "earliest",
+    hideTimeline: false,
+    colorScale: {
+        equalSizeBins: true,
+        binningStrategy: "ckmeans",
+        customNumericColorsActive: false,
+        colorSchemeInvert: false,
+        binningStrategyBinCount: 5,
+    },
+    scatterPointLabelStrategy: "year",
+    selectedFacetStrategy: "none",
+    invertColorScheme: false,
+    hideRelativeToggle: true,
+    logo: "owid",
+    entityType: "country or region",
+    facettingLabelByYVariables: "metric",
+    addCountryMode: "add-country",
+    compareEndPointsOnly: false,
+    type: "LineChart",
+    hasMapTab: false,
+    stackMode: "absolute",
+    minTime: "earliest",
+    hideAnnotationFieldsInTitle: {
+        entity: false,
+        time: false,
+        changeInPrefix: false,
+    },
+    xAxis: {
+        removePointsOutsideDomain: false,
+        min: "auto",
+        scaleType: "linear",
+        max: "auto",
+        canChangeScaleType: false,
+        facetDomain: "shared",
+    },
+    timelineMaxTime: "latest",
+    hideConnectedScatterLines: false,
+    showNoDataArea: true,
+    zoomToSelection: false,
+    showYearLabels: false,
+    hideTotalValueLabel: false,
+    hideScatterLabels: false,
+    sortBy: "total",
+    sortOrder: "desc",
+    hideFacetControl: true,
+    entityTypePlural: "countries and regions",
+    missingDataStrategy: "auto",
+}
diff --git a/packages/@ourworldindata/grapher/src/axis/AxisConfig.test.ts b/packages/@ourworldindata/grapher/src/axis/AxisConfig.test.ts
index cd8f5f25baa..9d4bd130dda 100755
--- a/packages/@ourworldindata/grapher/src/axis/AxisConfig.test.ts
+++ b/packages/@ourworldindata/grapher/src/axis/AxisConfig.test.ts
@@ -3,15 +3,15 @@
 import { AxisConfig } from "../axis/AxisConfig"
 import { ScaleType } from "@ourworldindata/types"
 
-it("serializes max to 'auto' if undefined", () => {
-    const axis = new AxisConfig({ min: 1 })
+it("serializes max to 'auto' if -Infinity", () => {
+    const axis = new AxisConfig({ min: 1, max: -Infinity })
     const obj = axis.toObject()
     expect(obj.min).toBe(1)
     expect(obj.max).toBe("auto")
 })
 
-it("serializes min to 'auto' if undefined", () => {
-    const axis = new AxisConfig({ max: 0 })
+it("serializes min to 'auto' if Infinity", () => {
+    const axis = new AxisConfig({ max: 0, min: Infinity })
     const obj = axis.toObject()
     expect(obj.max).toBe(0)
     expect(obj.min).toBe("auto")
diff --git a/packages/@ourworldindata/grapher/src/axis/AxisConfig.ts b/packages/@ourworldindata/grapher/src/axis/AxisConfig.ts
index 2226665d24c..676da96add0 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 a7713038b1f..47a3620b927 100644
--- a/packages/@ourworldindata/grapher/src/lineCharts/LineChart.tsx
+++ b/packages/@ourworldindata/grapher/src/lineCharts/LineChart.tsx
@@ -1344,6 +1344,8 @@ 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 6497d08f13c..dd0f68334e2 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 79ca82b4122..4465a68f6c0 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