diff --git a/packages/block-library/src/cover-image/editor.scss b/packages/block-library/src/cover-image/editor.scss
index d62d5806fd3b7..bc55badc130be 100644
--- a/packages/block-library/src/cover-image/editor.scss
+++ b/packages/block-library/src/cover-image/editor.scss
@@ -1,6 +1,4 @@
 .wp-block-cover-image {
-	margin: 0;
-
 	.editor-rich-text__tinymce[data-is-empty="true"]::before {
 		position: inherit;
 	}
diff --git a/packages/block-library/src/gallery/editor.scss b/packages/block-library/src/gallery/editor.scss
index 8a2aa5a51feaf..e4b82f3c4e59d 100644
--- a/packages/block-library/src/gallery/editor.scss
+++ b/packages/block-library/src/gallery/editor.scss
@@ -1,19 +1,3 @@
-.wp-block-gallery.components-placeholder {
-	margin: 0;
-}
-
-// Allow gallery items to go edge to edge.
-.gutenberg .wp-block-gallery:not(.components-placeholder) {
-	margin-left: -8px;
-	margin-right: -8px;
-}
-
-// Don't use negative margins when full-wide.
-.gutenberg [data-align="full"] .wp-block-gallery:not(.components-placeholder) {
-	margin-left: auto;
-	margin-right: auto;
-}
-
 .blocks-gallery-item {
 
 	// Hide the focus outline that otherwise briefly appears when selecting a block.
diff --git a/packages/block-library/src/gallery/style.scss b/packages/block-library/src/gallery/style.scss
index 3b91a9a39a5a1..dca2d13262691 100644
--- a/packages/block-library/src/gallery/style.scss
+++ b/packages/block-library/src/gallery/style.scss
@@ -4,12 +4,10 @@
 	list-style-type: none;
 	padding: 0;
 
-	// Allow gallery items to go edge to edge.
-	margin: 0 -8px 0 -8px;
-
 	.blocks-gallery-image,
 	.blocks-gallery-item {
-		margin: 8px;
+		// Add space between thumbnails, and unset right most thumbnails later.
+		margin: 0 $grid-size-large $grid-size-large 0;
 		display: flex;
 		flex-grow: 1;
 		flex-direction: column;
@@ -80,24 +78,48 @@
 		}
 	}
 
-	// Responsive fallback value, 2 columns
+	// On mobile and responsive viewports, we allow only 1 or 2 columns at the most.
 	& .blocks-gallery-image,
 	& .blocks-gallery-item {
-		width: calc(100% / 2 - 16px);
+		width: calc((100% - #{ $grid-size-large }) / 2);
+
+		&:nth-of-type(even) {
+			margin-right: 0;
+		}
 	}
 
 	&.columns-1 .blocks-gallery-image,
 	&.columns-1 .blocks-gallery-item {
-		width: calc(100% / 1 - 16px);
+		width: 100%;
+		margin-right: 0;
 	}
 
+	// Beyond mobile viewports, we allow up to 8 columns.
 	@include break-small {
 		@for $i from 3 through 8 {
 			&.columns-#{ $i } .blocks-gallery-image,
 			&.columns-#{ $i } .blocks-gallery-item {
-				width: calc(100% / #{ $i } - 16px);
+				width: calc((100% - #{ $grid-size-large } * #{ $i - 1 }) / #{ $i });
+				margin-right: 16px;
 			}
 		}
+
+		// Unset the right margin on every rightmost gallery item to ensure center balance.
+		@for $column-count from 1 through 8 {
+			&.columns-#{ $column-count } .blocks-gallery-image:nth-of-type(#{ $column-count }n),
+			&.columns-#{ $column-count } .blocks-gallery-item:nth-of-type(#{ $column-count }n) {
+				margin-right: 0;
+			}
+		}
+	}
+
+	// Last item always needs margins reset.
+	// When block is selected, only reset the right margin of the 2nd to last item.
+	.blocks-gallery-image:last-child,
+	.blocks-gallery-item:last-child,
+	.is-selected & .blocks-gallery-image:nth-last-child(2),
+	.is-selected & .blocks-gallery-item:nth-last-child(2) {
+		margin-right: 0;
 	}
 
 	// Make the "Add new Gallery item" button full-width (so it always appears
@@ -108,7 +130,7 @@
 		}
 	}
 
-	// Apply max-width to floated items that have no intrinsic width
+	// Apply max-width to floated items that have no intrinsic width.
 	[data-align="left"] &,
 	[data-align="right"] &,
 	&.alignleft,
diff --git a/packages/block-library/src/image/editor.scss b/packages/block-library/src/image/editor.scss
index 1c001538117ed..d2774299b3521 100644
--- a/packages/block-library/src/image/editor.scss
+++ b/packages/block-library/src/image/editor.scss
@@ -1,6 +1,5 @@
 .wp-block-image {
 	position: relative;
-	margin: 0;
 
 	&.is-transient img {
 		@include loading_fade;
diff --git a/packages/components/src/placeholder/style.scss b/packages/components/src/placeholder/style.scss
index 2ba60b2ab5d0c..62d23e704bbd6 100644
--- a/packages/components/src/placeholder/style.scss
+++ b/packages/components/src/placeholder/style.scss
@@ -1,4 +1,5 @@
 .components-placeholder {
+	margin: 0;
 	display: flex;
 	flex-direction: column;
 	align-items: center;