diff --git a/superset-frontend/plugins/plugin-chart-echarts/src/Timeseries/transformers.ts b/superset-frontend/plugins/plugin-chart-echarts/src/Timeseries/transformers.ts
index 78c1222a1fc6..a7a40ddaa079 100644
--- a/superset-frontend/plugins/plugin-chart-echarts/src/Timeseries/transformers.ts
+++ b/superset-frontend/plugins/plugin-chart-echarts/src/Timeseries/transformers.ts
@@ -472,6 +472,7 @@ export function transformFormulaAnnotation(
   return {
     name,
     id: name,
+    z: 10,
     itemStyle: {
       color: color || colorScale(name, sliceId),
     },
@@ -565,6 +566,7 @@ export function transformIntervalAnnotation(
     id: `Interval - ${name}`,
     type: 'line',
     animation: false,
+    z: 10,
     markArea: {
       silent: false,
       itemStyle: {
@@ -660,6 +662,7 @@ export function transformEventAnnotation(
     id: `Event - ${name}`,
     type: 'line',
     animation: false,
+    z: 10,
     markLine: {
       silent: false,
       symbol: 'none',
@@ -705,6 +708,7 @@ export function transformTimeseriesAnnotation(
       type: 'line',
       id: name,
       name,
+      z: 10,
       data,
       symbolSize: showMarkers ? markerSize : 0,
       itemStyle: computedStyle,
diff --git a/superset-frontend/plugins/plugin-chart-echarts/src/constants.ts b/superset-frontend/plugins/plugin-chart-echarts/src/constants.ts
index f496b7e2af81..3044bf10d704 100644
--- a/superset-frontend/plugins/plugin-chart-echarts/src/constants.ts
+++ b/superset-frontend/plugins/plugin-chart-echarts/src/constants.ts
@@ -122,4 +122,8 @@ export const TOOLTIP_POINTER_MARGIN = 10;
 // from the edge of the window should the tooltip be kept
 export const TOOLTIP_OVERFLOW_MARGIN = 5;
 
+// Minimum distance from the top of the chart container to keep the tooltip,
+// reserving space for annotation labels rendered at insideEndTop of markLines/markAreas
+export const TOOLTIP_TOP_CLEARANCE = 40;
+
 export const DEFAULT_LOCALE = 'en';
diff --git a/superset-frontend/plugins/plugin-chart-echarts/src/utils/tooltip.ts b/superset-frontend/plugins/plugin-chart-echarts/src/utils/tooltip.ts
index 59aaf63b0d7c..4fe0c16be519 100644
--- a/superset-frontend/plugins/plugin-chart-echarts/src/utils/tooltip.ts
+++ b/superset-frontend/plugins/plugin-chart-echarts/src/utils/tooltip.ts
@@ -24,7 +24,11 @@ import {
   getColumnLabel,
   getMetricLabel,
 } from '@superset-ui/core';
-import { TOOLTIP_OVERFLOW_MARGIN, TOOLTIP_POINTER_MARGIN } from '../constants';
+import {
+  TOOLTIP_OVERFLOW_MARGIN,
+  TOOLTIP_POINTER_MARGIN,
+  TOOLTIP_TOP_CLEARANCE,
+} from '../constants';
 import { Refs } from '../types';
 
 export function getDefaultTooltip(refs: Refs) {
@@ -107,18 +111,39 @@ export function getDefaultTooltip(refs: Refs) {
         }
       }
 
-      // Position tooltip above cursor, or below if no space
-      yPos = mouseY - TOOLTIP_POINTER_MARGIN - effectiveTooltipHeight;
+      // Mirror horizontal logic: position tooltip below cursor when in top half of chart,
+      // above cursor when in bottom half. This prevents the tooltip from covering annotation
+      // labels that appear at the top of the chart (markArea/markLine labels).
+      const chartHeight = divRect?.height || viewportHeight;
+      const cursorYInChart = canvasMousePos[1];
+      const isInTopHalfOfChart = cursorYInChart < chartHeight / 2;
 
-      // The tooltip is overflowing past the top edge of the window
-      if (yPos <= 0) {
-        // Attempt to place the tooltip to the bottom of the mouse position
+      if (isInTopHalfOfChart) {
         yPos = mouseY + TOOLTIP_POINTER_MARGIN;
 
-        // The tooltip is overflowing past the bottom edge of the window
-        if (yPos + effectiveTooltipHeight >= viewportHeight)
-          // Place the tooltip a fixed distance from the top edge of the window
-          yPos = TOOLTIP_OVERFLOW_MARGIN;
+        if (yPos + effectiveTooltipHeight >= viewportHeight) {
+          yPos = mouseY - TOOLTIP_POINTER_MARGIN - effectiveTooltipHeight;
+
+          if (yPos <= 0) {
+            yPos = TOOLTIP_OVERFLOW_MARGIN;
+          }
+        }
+      } else {
+        yPos = mouseY - TOOLTIP_POINTER_MARGIN - effectiveTooltipHeight;
+
+        if (yPos <= 0) {
+          yPos = mouseY + TOOLTIP_POINTER_MARGIN;
+
+          if (yPos + effectiveTooltipHeight >= viewportHeight) {
+            yPos = TOOLTIP_OVERFLOW_MARGIN;
+          }
+        }
+      }
+
+      // Clamp tooltip away from the top of the chart to avoid covering annotation labels
+      // (markLine/markArea labels rendered at insideEndTop are within the first ~40px)
+      if (divRect) {
+        yPos = Math.max(yPos, divRect.y + TOOLTIP_TOP_CLEARANCE);
       }
 
       // Return the position (converted back to a relative position on the canvas)