How to hide y axis line in ChartJs?

This disables the vertical Y axis line:

options: {
  scales: {
    yAxes: [{
      gridLines: {
        drawBorder: false,
      },
    }]
  },
},

This can be combined with display to disable the vertical gridLines:

xAxes: [{
  gridLines: {
    display: false,
  },
}],

Here's a working example: http://codepen.io/anon/pen/xqGGaV

var myBubbleChart = new Chart(ctx,{
    type: 'bubble',
    data: data,
    options: {
        scales:
        {
            yAxes: [{
                gridLines : {
                    display : false
                }
            }]
        }
    }
});

From version 3 upwards, you should use this options to hide axes completely:

Picture: chartjs-without-axes

scales: {
   x: {
      display: false,
   },
   y: {
      display: false,
   }
},

For Chartjs version 3.3.2 this works for me

var barChart = new Chart(ctx,{
    type: 'bar',
    data: data,
    options: {
        scales:
        {
            y: {
                grid: {
                    drawBorder: false, // <-- this removes y-axis line
                    lineWidth: 0.5,
                }
            }
        }
    }
});