diff --git a/assets/sass/_variables.scss b/assets/sass/_variables.scss
index 71cbe5a..dc7852c 100644
--- a/assets/sass/_variables.scss
+++ b/assets/sass/_variables.scss
@@ -3,6 +3,10 @@
     --color-foreground: #D3D7CF;
     --color-blue-light: #9CD9F0;
     --color-blue-dark: #72B3CC;
+    --color-green-light: #CDEE69;
+    --color-green-dark: #8EB33B;
+    --color-yellow-light: #FFE377;
+    --color-yellow-dark: #D0B03C;
     --color-black-light: #5D5D5D;
     --color-black-dark: #000000;
     --color-white-light: #F7F7F7;
diff --git a/assets/sass/components/_content.scss b/assets/sass/components/_content.scss
index 8b51a5e..7eb90d8 100644
--- a/assets/sass/components/_content.scss
+++ b/assets/sass/components/_content.scss
@@ -5,4 +5,5 @@ body > main {
     }
 }
 
+@import 'content/flash';
 @import 'content/entries';
diff --git a/assets/sass/components/content/_flash.scss b/assets/sass/components/content/_flash.scss
new file mode 100644
index 0000000..430d1d2
--- /dev/null
+++ b/assets/sass/components/content/_flash.scss
@@ -0,0 +1,20 @@
+body > aside {
+    ul {
+        list-style: none;
+        color: var(--color-black-dark);
+        margin: var(--spacing-elements);
+
+        li {
+            padding: var(--spacing-small-elements);
+        }
+
+        &.success {
+            background-color: var(--color-green-dark);
+            border: var(--color-green-light) solid var(--width-border-default);
+        }
+        &.notice {
+            background-color: var(--color-yellow-dark);
+            border: var(--color-yellow-light) solid var(--width-border-default);
+        }
+    }
+}
diff --git a/config/routes.yaml b/config/routes.yaml
index f6d5ae1..33d8948 100644
--- a/config/routes.yaml
+++ b/config/routes.yaml
@@ -17,3 +17,11 @@ feed:
 entry:
     path: /entry/{slug}
     controller: App\Controller\EntryController::show
+
+entry-mark-as-read:
+    path: /entry/{slug}/mark/read
+    controller: App\Controller\EntryController::read
+
+entry-mark-as-un-read:
+    path: /entry/{slug}/mark/un-read
+    controller: App\Controller\EntryController::unRead
diff --git a/public/css/style.css b/public/css/style.css
index 208e190..a832f3e 100644
--- a/public/css/style.css
+++ b/public/css/style.css
@@ -3,6 +3,10 @@
   --color-foreground: #D3D7CF;
   --color-blue-light: #9CD9F0;
   --color-blue-dark: #72B3CC;
+  --color-green-light: #CDEE69;
+  --color-green-dark: #8EB33B;
+  --color-yellow-light: #FFE377;
+  --color-yellow-dark: #D0B03C;
   --color-black-light: #5D5D5D;
   --color-black-dark: #000000;
   --color-white-light: #F7F7F7;
@@ -56,6 +60,19 @@ body > main {
   body > main header h1 {
     margin: 0; }
 
+body > aside ul {
+  list-style: none;
+  color: var(--color-black-dark);
+  margin: var(--spacing-elements); }
+  body > aside ul li {
+    padding: var(--spacing-small-elements); }
+  body > aside ul.success {
+    background-color: var(--color-green-dark);
+    border: var(--color-green-light) solid var(--width-border-default); }
+  body > aside ul.notice {
+    background-color: var(--color-yellow-dark);
+    border: var(--color-yellow-light) solid var(--width-border-default); }
+
 article {
   display: grid;
   grid-template-columns: 50em var(--width-sidebar-max);
diff --git a/src/Controller/EntryController.php b/src/Controller/EntryController.php
index f579517..08e18cd 100644
--- a/src/Controller/EntryController.php
+++ b/src/Controller/EntryController.php
@@ -3,14 +3,64 @@
 namespace App\Controller;
 
 use App\Entity\Entry;
+use Doctrine\ORM\EntityManagerInterface;
 use Symfony\Bundle\FrameworkBundle\Controller\AbstractController;
+use Symfony\Component\HttpFoundation\Request;
+use Symfony\Component\HttpFoundation\Response;
 
 class EntryController extends AbstractController
 {
-    public function show(Entry $entry)
+    /**
+     * @var EntityManagerInterface
+     */
+    private $entityManager;
+
+    public function __construct(
+        EntityManagerInterface $entityManager
+    ) {
+        $this->entityManager = $entityManager;
+    }
+
+    public function show(Entry $entry): Response
     {
         return $this->render('entry/show.html.twig', [
             'entry' => $entry,
         ]);
     }
+
+    public function read(Entry $entry, Request $request): Response
+    {
+        if ($entry->wasRead()) {
+            $this->addFlash('notice', sprintf('Entry "%s" was already marked as read.', $entry->getName()));
+        } else {
+            $entry->markAsRead();
+            $this->entityManager->flush();
+            $this->addFlash('success', sprintf('Entry "%s" was marked as read.', $entry->getName()));
+        }
+
+        return $this->getRedirectResponseAfterModification($request);
+    }
+
+    public function unRead(Entry $entry, Request $request): Response
+    {
+        if ($entry->wasRead()) {
+            $entry->markAsUnRead();
+            $this->entityManager->flush();
+            $this->addFlash('success', sprintf('Entry "%s" was marked as un read.', $entry->getName()));
+        } else {
+            $this->addFlash('notice', sprintf('Entry "%s" was not yet marked as read.', $entry->getName()));
+        }
+
+        return $this->getRedirectResponseAfterModification($request);
+    }
+
+    private function getRedirectResponseAfterModification(Request $request): Response
+    {
+        $redirectTarget = $request->headers->get('referer');
+        if (is_string($redirectTarget)) {
+            return $this->redirect($redirectTarget, 307);
+        }
+
+        return $this->redirectToRoute('start', [], 307);
+    }
 }
diff --git a/src/Entity/Bucket.php b/src/Entity/Bucket.php
index 582a16a..3410451 100644
--- a/src/Entity/Bucket.php
+++ b/src/Entity/Bucket.php
@@ -5,6 +5,7 @@ namespace App\Entity;
 use App\Repository\BucketRepository;
 use Doctrine\Common\Collections\ArrayCollection;
 use Doctrine\Common\Collections\Collection;
+use Doctrine\Common\Collections\Criteria;
 use Doctrine\ORM\Mapping as ORM;
 
 /**
@@ -59,9 +60,6 @@ class Bucket
         return $this->slug;
     }
 
-    /**
-     * @return Collection|Feed[]
-     */
     public function getFeeds(): Collection
     {
         return $this->feeds;
diff --git a/src/Entity/Entry.php b/src/Entity/Entry.php
index 1c5c40c..66d15c9 100644
--- a/src/Entity/Entry.php
+++ b/src/Entity/Entry.php
@@ -128,9 +128,18 @@ class Entry
         return $this->content;
     }
 
-    // TODO: Rename into is / was ?
-    public function getRead(): bool
+    public function wasRead(): bool
     {
         return $this->read;
     }
+
+    public function markAsRead(): void
+    {
+        $this->read = true;
+    }
+
+    public function markAsUnRead(): void
+    {
+        $this->read = false;
+    }
 }
diff --git a/src/Entity/Feed.php b/src/Entity/Feed.php
index fce96fd..38de218 100644
--- a/src/Entity/Feed.php
+++ b/src/Entity/Feed.php
@@ -5,6 +5,7 @@ namespace App\Entity;
 use App\Repository\FeedRepository;
 use Doctrine\Common\Collections\ArrayCollection;
 use Doctrine\Common\Collections\Collection;
+use Doctrine\Common\Collections\Criteria;
 use Doctrine\ORM\Mapping as ORM;
 
 /**
@@ -100,4 +101,11 @@ class Feed
     {
         return $this->entries;
     }
+
+    public function getUnreadEntries(): Collection
+    {
+        $criteria = Criteria::create();
+        $criteria->where(Criteria::expr()->eq('read', false));
+        return $this->entries->matching($criteria);
+    }
 }
diff --git a/templates/base.html.twig b/templates/base.html.twig
index 650e014..82bb885 100644
--- a/templates/base.html.twig
+++ b/templates/base.html.twig
@@ -12,6 +12,16 @@
             <h1><a href="{{ path('start') }}">{{ app_name }}</a></h1>
         </header>
 
+        <aside>
+            {% for label, messages in app.flashes %}
+                <ul class="{{ label }}">
+                    {% for message in messages %}
+                        <li>{{ message }}</li>
+                    {% endfor %}
+                </ul>
+            {% endfor %}
+        </aside>
+
         <main>
             {% block body %}{% endblock %}
         </main>
diff --git a/templates/bucket/show.html.twig b/templates/bucket/show.html.twig
index 67648bb..f8ed1e6 100644
--- a/templates/bucket/show.html.twig
+++ b/templates/bucket/show.html.twig
@@ -9,7 +9,7 @@
     </header>
 
     {# TODO: collect newest entries of all feeds in controller #}
-    {{ include('feed/entries.html.twig', {entries: bucket.feeds.first.entries | slice(0, 10) }) }}
+    {{ include('feed/entries.html.twig', {entries: bucket.feeds.first.unreadEntries | slice(0, 10) }) }}
 
     <aside>
         <h1>Feeds in this bucket</h1>
diff --git a/templates/entry/_single.html.twig b/templates/entry/_single.html.twig
index 0a1aa51..4a5ff33 100644
--- a/templates/entry/_single.html.twig
+++ b/templates/entry/_single.html.twig
@@ -28,5 +28,11 @@
 
         <a href="{{ path('bucket', {slug: entry.feed.bucket.slug}) }}">{{ entry.feed.bucket.name }} bucket</a>
         <a href="{{ path('feed', {slug: entry.feed.slug}) }}">{{ entry.feed.name }} feed</a>
+
+        {% if entry.wasRead %}
+            <a href="{{ path('entry-mark-as-un-read', {slug: entry.slug}) }}">Mark as unread</a>
+        {% else %}
+            <a href="{{ path('entry-mark-as-read', {slug: entry.slug}) }}">Mark as read</a>
+        {% endif %}
     </nav>
 </article>
diff --git a/templates/feed/entries.html.twig b/templates/feed/entries.html.twig
index cbab705..723fac3 100644
--- a/templates/feed/entries.html.twig
+++ b/templates/feed/entries.html.twig
@@ -1,3 +1,7 @@
-{% for entry in entries %}
-    {{ include('entry/_single.html.twig', {entry: entry, short: true}) }}
-{% endfor %}
+{% if entries %}
+    {% for entry in entries %}
+        {{ include('entry/_single.html.twig', {entry: entry, short: true}) }}
+    {% endfor %}
+{% else %}
+    No unread entries in this feed.
+{% endif %}
diff --git a/templates/feed/show.html.twig b/templates/feed/show.html.twig
index c00cad7..e36c788 100644
--- a/templates/feed/show.html.twig
+++ b/templates/feed/show.html.twig
@@ -21,6 +21,6 @@
         </nav>
     </header>
 
-    {{ include('feed/entries.html.twig', {entries: feed.entries}) }}
+    {{ include('feed/entries.html.twig', {entries: feed.unreadEntries}) }}
 
 {% endblock %}