diff --git a/src/components/annotations/attributes.js b/src/components/annotations/attributes.js
index a2eaf49d45d..cea6afb9a4a 100644
--- a/src/components/annotations/attributes.js
+++ b/src/components/annotations/attributes.js
@@ -137,8 +137,10 @@ module.exports = {
         role: 'info',
         description: [
             'Sets the x component of the arrow tail about the arrow head.',
-            'A positive (negative) component corresponds to an arrow pointing',
-            'from right to left (left to right)'
+            'If `axref` is `pixel`, a positive (negative) ',
+            'component corresponds to an arrow pointing',
+            'from right to left (left to right).',
+            'If `axref` is an axis, this is a value on that axis.'
         ].join(' ')
     },
     ay: {
@@ -147,8 +149,44 @@ module.exports = {
         role: 'info',
         description: [
             'Sets the y component of the arrow tail about the arrow head.',
-            'A positive (negative) component corresponds to an arrow pointing',
-            'from bottom to top (top to bottom)'
+            'If `ayref` is `pixel`, a positive (negative) ',
+            'component corresponds to an arrow pointing',
+            'from bottom to top (top to bottom).',
+            'If `ayref` is an axis, this is a value on that axis.'
+        ].join(' ')
+    },
+    axref: {
+        valType: 'enumerated',
+        dflt: 'pixel',
+        values: [
+            'pixel',
+            cartesianConstants.idRegex.x.toString()
+        ],
+        role: 'info',
+        description: [
+            'Indicates in what terms the tail of the annotation (ax,ay) ',
+            'is specified. If `pixel`, `ax` is a relative offset in pixels ',
+            'from `x`. If set to an x axis id (e.g. *x* or *x2*), `ax` is ',
+            'specified in the same terms as that axis. This is useful ',
+            'for trendline annotations which should continue to indicate ',
+            'the correct trend when zoomed.'
+        ].join(' ')
+    },
+    ayref: {
+        valType: 'enumerated',
+        dflt: 'pixel',
+        values: [
+            'pixel',
+            cartesianConstants.idRegex.y.toString()
+        ],
+        role: 'info',
+        description: [
+            'Indicates in what terms the tail of the annotation (ax,ay) ',
+            'is specified. If `pixel`, `ay` is a relative offset in pixels ',
+            'from `y`. If set to a y axis id (e.g. *y* or *y2*), `ay` is ',
+            'specified in the same terms as that axis. This is useful ',
+            'for trendline annotations which should continue to indicate ',
+            'the correct trend when zoomed.'
         ].join(' ')
     },
     // positioning
diff --git a/src/components/annotations/index.js b/src/components/annotations/index.js
index 60385078844..3fc49527908 100644
--- a/src/components/annotations/index.js
+++ b/src/components/annotations/index.js
@@ -59,6 +59,8 @@ function handleAnnotationDefaults(annIn, fullLayout) {
         coerce('arrowwidth', ((borderOpacity && borderWidth) || 1) * 2);
         coerce('ax');
         coerce('ay');
+        coerce('axref');
+        coerce('ayref');
 
         // if you have one part of arrow length you should have both
         Lib.noneOrAll(annIn, annOut, ['ax', 'ay']);
@@ -76,6 +78,10 @@ function handleAnnotationDefaults(annIn, fullLayout) {
         // xref, yref
         var axRef = Axes.coerceRef(annIn, annOut, tdMock, axLetter);
 
+        //todo: should be refactored in conjunction with Axes
+        // axref, ayref
+        var aaxRef = Axes.coerceARef(annIn, annOut, tdMock, axLetter);
+
         // x, y
         var defaultPosition = 0.5;
         if(axRef !== 'paper') {
@@ -89,6 +95,11 @@ function handleAnnotationDefaults(annIn, fullLayout) {
                 if(ax.type === 'date') {
                     newval = Lib.dateTime2ms(annIn[axLetter]);
                     if(newval !== false) annIn[axLetter] = newval;
+
+                    if(aaxRef === axRef) {
+                        var newvalB = Lib.dateTime2ms(annIn['a' + axLetter]);
+                        if(newvalB !== false) annIn['a' + axLetter] = newvalB;
+                    }
                 }
                 else if((ax._categories || []).length) {
                     newval = ax._categories.indexOf(annIn[axLetter]);
@@ -419,8 +430,8 @@ annotations.draw = function(gd, index, opt, value) {
 
         var annotationIsOffscreen = false;
         ['x', 'y'].forEach(function(axLetter) {
-            var ax = Axes.getFromId(gd,
-                    options[axLetter + 'ref'] || axLetter),
+            var axRef = options[axLetter + 'ref'] || axLetter,
+                ax = Axes.getFromId(gd, axRef),
                 dimAngle = (textangle + (axLetter === 'x' ? 0 : 90)) * Math.PI / 180,
                 annSize = outerwidth * Math.abs(Math.cos(dimAngle)) +
                           outerheight * Math.abs(Math.sin(dimAngle)),
@@ -435,8 +446,16 @@ annotations.draw = function(gd, index, opt, value) {
                 // anyway to get its bounding box)
                 if(!ax.autorange && ((options[axLetter] - ax.range[0]) *
                                      (options[axLetter] - ax.range[1]) > 0)) {
-                    annotationIsOffscreen = true;
-                    return;
+                    if(options['a' + axLetter + 'ref'] === axRef) {
+                        if((options['a' + axLetter] - ax.range[0]) *
+                            (options['a' + axLetter] - ax.range[1]) > 0) {
+                            annotationIsOffscreen = true;
+                        }
+                    } else {
+                        annotationIsOffscreen = true;
+                    }
+
+                    if(annotationIsOffscreen) return;
                 }
                 annPosPx[axLetter] = ax._offset + ax.l2p(options[axLetter]);
                 alignPosition = 0.5;
@@ -450,13 +469,17 @@ annotations.draw = function(gd, index, opt, value) {
             }
 
             var alignShift = 0;
-            if(options.showarrow) {
-                alignShift = options['a' + axLetter];
-            }
-            else {
-                alignShift = annSize * shiftFraction(alignPosition, anchor);
+            if(options['a' + axLetter + 'ref'] === axRef) {
+                annPosPx['aa' + axLetter] = ax._offset + ax.l2p(options['a' + axLetter]);
+            } else {
+                if(options.showarrow) {
+                    alignShift = options['a' + axLetter];
+                }
+                else {
+                    alignShift = annSize * shiftFraction(alignPosition, anchor);
+                }
+                annPosPx[axLetter] += alignShift;
             }
-            annPosPx[axLetter] += alignShift;
 
             // save the current axis type for later log/linear changes
             options['_' + axLetter + 'type'] = ax && ax.type;
@@ -476,8 +499,21 @@ annotations.draw = function(gd, index, opt, value) {
         // make sure the arrowhead (if there is one)
         // and the annotation center are visible
         if(options.showarrow) {
-            arrowX = Lib.constrain(annPosPx.x - options.ax, 1, fullLayout.width - 1);
-            arrowY = Lib.constrain(annPosPx.y - options.ay, 1, fullLayout.height - 1);
+            if(options.axref === options.xref) {
+                //we don't want to constrain if the tail is absolute
+                //or the slope (which is meaningful) will change.
+                arrowX = annPosPx.x;
+            } else {
+                arrowX = Lib.constrain(annPosPx.x - options.ax, 1, fullLayout.width - 1);
+            }
+
+            if(options.ayref === options.yref) {
+                //we don't want to constrain if the tail is absolute
+                //or the slope (which is meaningful) will change.
+                arrowY = annPosPx.y;
+            } else {
+                arrowY = Lib.constrain(annPosPx.y - options.ay, 1, fullLayout.height - 1);
+            }
         }
         annPosPx.x = Lib.constrain(annPosPx.x, 1, fullLayout.width - 1);
         annPosPx.y = Lib.constrain(annPosPx.y, 1, fullLayout.height - 1);
@@ -496,8 +532,19 @@ annotations.draw = function(gd, index, opt, value) {
         annbg.call(Drawing.setRect, borderwidth / 2, borderwidth / 2,
             outerwidth - borderwidth, outerheight - borderwidth);
 
-        var annX = Math.round(annPosPx.x - outerwidth / 2),
+        var annX = 0, annY = 0;
+        if(options.axref === options.xref) {
+            annX = Math.round(annPosPx.aax - outerwidth / 2);
+        } else {
+            annX = Math.round(annPosPx.x - outerwidth / 2);
+        }
+
+        if(options.ayref === options.yref) {
+            annY = Math.round(annPosPx.aay - outerheight / 2);
+        } else {
             annY = Math.round(annPosPx.y - outerheight / 2);
+        }
+
         ann.call(Lib.setTranslate, annX, annY);
 
         var annbase = 'annotations[' + index + ']';
@@ -515,11 +562,22 @@ annotations.draw = function(gd, index, opt, value) {
             // looks like there may be a cross-browser solution, see
             // http://stackoverflow.com/questions/5364980/
             //    how-to-get-the-width-of-an-svg-tspan-element
-            var arrowX0 = annPosPx.x + dx,
-                arrowY0 = annPosPx.y + dy,
+            var arrowX0, arrowY0;
+
+            if(options.axref === options.xref) {
+                arrowX0 = annPosPx.aax + dx;
+            } else {
+                arrowX0 = annPosPx.x + dx;
+            }
+
+            if(options.ayref === options.yref) {
+                arrowY0 = annPosPx.aay + dy;
+            } else {
+                arrowY0 = annPosPx.y + dy;
+            }
 
                 // create transform matrix and related functions
-                transform =
+            var transform =
                     Lib.rotationXYMatrix(textangle, arrowX0, arrowY0),
                 applyTransform = Lib.apply2DTransform(transform),
                 applyTransform2 = Lib.apply2DTransform2(transform),
@@ -618,6 +676,18 @@ annotations.draw = function(gd, index, opt, value) {
                             (options.y + dy / ya._m) :
                             (1 - ((arrowY + dy - gs.t) / gs.h));
 
+                        if(options.axref === options.xref) {
+                            update[annbase + '.ax'] = xa ?
+                              (options.ax + dx / xa._m) :
+                              ((arrowX + dx - gs.l) / gs.w);
+                        }
+
+                        if(options.ayref === options.yref) {
+                            update[annbase + '.ay'] = ya ?
+                              (options.ay + dy / ya._m) :
+                              (1 - ((arrowY + dy - gs.t) / gs.h));
+                        }
+
                         anng.attr({
                             transform: 'rotate(' + textangle + ',' +
                                    xcenter + ',' + ycenter + ')'
@@ -660,8 +730,18 @@ annotations.draw = function(gd, index, opt, value) {
                     ann.call(Lib.setTranslate, x0 + dx, y0 + dy);
                     var csr = 'pointer';
                     if(options.showarrow) {
-                        update[annbase + '.ax'] = options.ax + dx;
-                        update[annbase + '.ay'] = options.ay + dy;
+                        if(options.axref === options.xref) {
+                            update[annbase + '.ax'] = xa.p2l(xa.l2p(options.ax) + dx);
+                        } else {
+                            update[annbase + '.ax'] = options.ax + dx;
+                        }
+
+                        if(options.ayref === options.yref) {
+                            update[annbase + '.ay'] = ya.p2l(ya.l2p(options.ay) + dy);
+                        } else {
+                            update[annbase + '.ay'] = options.ay + dy;
+                        }
+
                         drawArrow(dx, dy);
                     }
                     else {
diff --git a/src/plots/cartesian/axes.js b/src/plots/cartesian/axes.js
index fc0c4c2ea4a..4db4ca2c642 100644
--- a/src/plots/cartesian/axes.js
+++ b/src/plots/cartesian/axes.js
@@ -55,6 +55,26 @@ axes.coerceRef = function(containerIn, containerOut, gd, axLetter, dflt) {
     return Lib.coerce(containerIn, containerOut, attrDef, refAttr);
 };
 
+//todo: duplicated per github PR 610. Should be consolidated with axes.coerceRef.
+// find the list of possible axes to reference with an axref or ayref attribute
+// and coerce it to that list
+axes.coerceARef = function(containerIn, containerOut, gd, axLetter, dflt) {
+    var axlist = gd._fullLayout._has('gl2d') ? [] : axes.listIds(gd, axLetter),
+        refAttr = 'a' + axLetter + 'ref',
+        attrDef = {};
+
+    // data-ref annotations are not supported in gl2d yet
+
+    attrDef[refAttr] = {
+        valType: 'enumerated',
+        values: axlist.concat(['pixel']),
+        dflt: dflt || 'pixel' || axlist[0]
+    };
+
+    // axref, ayref
+    return Lib.coerce(containerIn, containerOut, attrDef, refAttr);
+};
+
 // empty out types for all axes containing these traces
 // so we auto-set them again
 axes.clearTypes = function(gd, traces) {
diff --git a/test/image/baselines/annotations.png b/test/image/baselines/annotations.png
index 5edbbe7d1c5..056e5c86268 100644
Binary files a/test/image/baselines/annotations.png and b/test/image/baselines/annotations.png differ
diff --git a/test/image/mocks/annotations.json b/test/image/mocks/annotations.json
index 9eea27ff63e..9f88a7a5179 100644
--- a/test/image/mocks/annotations.json
+++ b/test/image/mocks/annotations.json
@@ -41,7 +41,9 @@
                 "bordercolor":"rgb(255, 0, 0)","borderwidth":4,"bgcolor":"rgba(255,255,0,0.5)",
                 "font":{"color":"rgb(0, 0, 255)","size":20},
                 "arrowcolor":"rgb(166, 28, 0)","borderpad":3,"textangle":50,"x":5,"y":1
-            }
+            },
+            {"text":"","showarrow":true,"borderwidth":1.2,"arrowhead":2,"axref":"x","ayref":"y","x":5,"y":3,"ax":4,"ay":5},
+            {"text":"","showarrow":true,"borderwidth":1.2,"arrowhead":2,"axref":"x","ayref":"y","x":6,"y":2,"ax":3,"ay":3}
         ]
     }
 }
diff --git a/test/jasmine/tests/annotations_test.js b/test/jasmine/tests/annotations_test.js
new file mode 100644
index 00000000000..3b6d02a75e6
--- /dev/null
+++ b/test/jasmine/tests/annotations_test.js
@@ -0,0 +1,33 @@
+require('@src/plotly');
+var Plots = require('@src/plots/plots');
+var Annotations = require('@src/components/annotations');
+var Dates = require('@src/lib/dates');
+
+describe('Test annotations', function() {
+    'use strict';
+
+    describe('supplyLayoutDefaults', function() {
+        it('should default to pixel for axref/ayref', function() {
+            var annotationDefaults = {};
+            annotationDefaults._has = Plots._hasPlotType.bind(annotationDefaults);
+
+            Annotations.supplyLayoutDefaults({ annotations: [{ showarrow: true, arrowhead: 2}] }, annotationDefaults);
+
+            expect(annotationDefaults.annotations[0].axref).toEqual('pixel');
+            expect(annotationDefaults.annotations[0].ayref).toEqual('pixel');
+        });
+
+        it('should convert ax/ay date coordinates to milliseconds if tail is in axis terms and axis is a date', function() {
+            var annotationOut = { xaxis: { type: 'date', range: ['2000-01-01', '2016-01-01'] }};
+            annotationOut._has = Plots._hasPlotType.bind(annotationOut);
+
+            var annotationIn = {
+                annotations: [{ showarrow: true, axref: 'x', ayref: 'y', x: '2008-07-01', ax: '2004-07-01', y: 0, ay: 50}]
+            };
+
+            Annotations.supplyLayoutDefaults(annotationIn, annotationOut);
+
+            expect(annotationIn.annotations[0].ax).toEqual(Dates.dateTime2ms('2004-07-01'));
+        });
+    });
+});