Stretch image to fit full container width bootstrap

Here's what worked for me. Note: Adding the image within a row introduces some space so I've intentionally used only a div to encapsulate the image.

<div class="container-fluid w-100 h-auto m-0 p-0">  

    <img src="someimg.jpg" class="img-fluid w-100 h-auto p-0 m-0" alt="Patience">           

</div>

First of all if the size of the image is smaller than the container, then only "img-fluid" class will not solve your problem. you have to set the width of image to 100%, for that you can use Bootstrap class "w-100". keep in mind that "container-fluid" and "col-12" class sets left and right padding to 15px and "row" class sets left and right margin to "-15px" by default. make sure to set them to 0.

Note: "px-0" is a bootstrap class which sets left and right padding to 0 and
"mx-0" is a bootstrap class which sets left and right margin to 0

P.S. i am using Bootstrap 4.0 version.

 <div class="container-fluid px-0">
        <div class="row mx-0">
            <div class="col-12 px-0">
            <img src="images/top.jpg" class="img-fluid w-100">
            </div>
        </div>
    </div>

Check if this solves the problem:

<div class="container-fluid no-padding">
  <div class="row">
    <div class="col-md-12">
      <img src="https://placeholdit.imgix.net/~text?txtsize=33&txt=1300%C3%97400&w=1300&h=400" alt="placeholder 960" class="img-responsive" />
    </div>
  </div>
</div>

CSS

.no-padding {
  padding-left: 0;
  padding-right: 0;
}

Css class no-padding will override default bootstrap container padding.

Full example here.

---

@Update If you use bootstrap 4 it could be done even simpler

<div class="container-fluid px-0">
  <div class="row">
    <div class="col-md-12">
      <img src="https://placeholdit.imgix.net/~text?txtsize=33&txt=1300%C3%97400&w=1300&h=400" alt="placeholder 960" class="img-responsive" />
    </div>
   </div>
</div>

Updated example here.

In bootstrap 4.1, the w-100 class is required along with img-fluid for images smaller than the page to be stretched:

<div class="container">
  <div class="row">
    <img class='img-fluid w-100' src="#" alt="" />
  </div>
</div>

see closed issue: https://github.com/twbs/bootstrap/issues/20830

(As of 2018-04-20, the documentation is wrong: https://getbootstrap.com/docs/4.1/content/images/ says that img-fluid applies max-width: 100%; height: auto;" but img-fluid does not resolve the issue, and neither does manually adding those style attributes with or without bootstrap classes on the img tag.)