diff --git a/packages/core/src/render3/instructions/element.ts b/packages/core/src/render3/instructions/element.ts
index c73cb8b03814b..b8be8c4e60064 100644
--- a/packages/core/src/render3/instructions/element.ts
+++ b/packages/core/src/render3/instructions/element.ts
@@ -10,7 +10,7 @@ import {assertDataInRange, assertDefined, assertEqual} from '../../util/assert';
 import {assertHasParent} from '../assert';
 import {attachPatchData} from '../context_discovery';
 import {registerPostOrderHooks} from '../hooks';
-import {TAttributes, TNodeFlags, TNodeType} from '../interfaces/node';
+import {TAttributes, TNode, TNodeFlags, TNodeType} from '../interfaces/node';
 import {RElement} from '../interfaces/renderer';
 import {StylingMapArray, TStylingContext} from '../interfaces/styling';
 import {isContentQueryHost, isDirectiveHost} from '../interfaces/type_checks';
@@ -22,7 +22,7 @@ import {setUpAttributes} from '../util/attrs_utils';
 import {getInitialStylingValue, hasClassInput, hasStyleInput, selectClassBasedInputName} from '../util/styling_utils';
 import {getNativeByTNode, getTNode} from '../util/view_utils';
 
-import {createDirectivesInstances, elementCreate, executeContentQueries, getOrCreateTNode, renderInitialStyling, resolveDirectives, saveResolvedLocalsInData, setInputsForProperty} from './shared';
+import {createDirectivesInstances, elementCreate, executeContentQueries, getOrCreateTNode, matchingSchemas, renderInitialStyling, resolveDirectives, saveResolvedLocalsInData, setInputsForProperty} from './shared';
 import {registerInitialStylingOnTNode} from './styling';
 
 
@@ -84,7 +84,8 @@ export function ɵɵelementStart(
   // and `[class]` bindings work for multiple directives.)
   if (tView.firstTemplatePass) {
     ngDevMode && ngDevMode.firstTemplatePass++;
-    resolveDirectives(tView, lView, tNode, localRefs || null);
+    const hasDirectives = resolveDirectives(tView, lView, tNode, localRefs || null);
+    ngDevMode && validateElement(lView, native, tNode, hasDirectives);
 
     if (tView.queries !== null) {
       tView.queries.elementStart(tView, tNode);
@@ -241,3 +242,33 @@ function setDirectiveStylingInput(
   // be (Jira Issue = FW-1467).
   setInputsForProperty(lView, stylingInputs, value);
 }
+
+function validateElement(
+    hostView: LView, element: RElement, tNode: TNode, hasDirectives: boolean): void {
+  const tagName = tNode.tagName;
+
+  // If the element matches any directive, it's considered as valid.
+  if (!hasDirectives && tagName !== null) {
+    // The element is unknown if it's an instance of HTMLUnknownElement or it isn't registered
+    // as a custom element. Note that unknown elements with a dash in their name won't be instances
+    // of HTMLUnknownElement in browsers that support web components.
+    const isUnknown =
+        (typeof HTMLUnknownElement === 'function' && element instanceof HTMLUnknownElement) ||
+        (typeof customElements !== 'undefined' && tagName.indexOf('-') > -1 &&
+         !customElements.get(tagName));
+
+    if (isUnknown && !matchingSchemas(hostView, tagName)) {
+      let errorMessage = `'${tagName}' is not a known element:\n`;
+      errorMessage +=
+          `1. If '${tagName}' is an Angular component, then verify that it is part of this module.\n`;
+      if (tagName && tagName.indexOf('-') > -1) {
+        errorMessage +=
+            `2. If '${tagName}' is a Web Component then add 'CUSTOM_ELEMENTS_SCHEMA' to the '@NgModule.schemas' of this component to suppress this message.`;
+      } else {
+        errorMessage +=
+            `2. To allow any element add 'NO_ERRORS_SCHEMA' to the '@NgModule.schemas' of this component.`;
+      }
+      throw new Error(errorMessage);
+    }
+  }
+}
diff --git a/packages/core/src/render3/instructions/shared.ts b/packages/core/src/render3/instructions/shared.ts
index c5cd3cde6d266..078f353235bbf 100644
--- a/packages/core/src/render3/instructions/shared.ts
+++ b/packages/core/src/render3/instructions/shared.ts
@@ -989,7 +989,7 @@ function validateProperty(
       isAnimationProp(propName) || typeof Node !== 'function' || !(element instanceof Node);
 }
 
-function matchingSchemas(hostView: LView, tagName: string | null): boolean {
+export function matchingSchemas(hostView: LView, tagName: string | null): boolean {
   const schemas = hostView[TVIEW].schemas;
 
   if (schemas !== null) {
@@ -1040,17 +1040,19 @@ export function instantiateRootComponent<T>(tView: TView, lView: LView, def: Com
  */
 export function resolveDirectives(
     tView: TView, lView: LView, tNode: TElementNode | TContainerNode | TElementContainerNode,
-    localRefs: string[] | null): void {
+    localRefs: string[] | null): boolean {
   // Please make sure to have explicit type for `exportsMap`. Inferred type triggers bug in
   // tsickle.
   ngDevMode && assertFirstTemplatePass(tView);
 
-  if (!getBindingsEnabled()) return;
+  if (!getBindingsEnabled()) return false;
 
   const directives: DirectiveDef<any>[]|null = findDirectiveMatches(tView, lView, tNode);
   const exportsMap: ({[key: string]: number} | null) = localRefs ? {'': -1} : null;
+  let hasDirectives = false;
 
   if (directives !== null) {
+    hasDirectives = true;
     initNodeFlags(tNode, tView.data.length, directives.length);
     // When the same token is provided by several directives on the same node, some rules apply in
     // the viewEngine:
@@ -1088,6 +1090,7 @@ export function resolveDirectives(
     initializeInputAndOutputAliases(tView, tNode);
   }
   if (exportsMap) cacheMatchingLocalNames(tNode, localRefs, exportsMap);
+  return hasDirectives;
 }
 
 /**
diff --git a/packages/core/test/acceptance/i18n_spec.ts b/packages/core/test/acceptance/i18n_spec.ts
index 99b184896a2f9..afab8754963d1 100644
--- a/packages/core/test/acceptance/i18n_spec.ts
+++ b/packages/core/test/acceptance/i18n_spec.ts
@@ -10,7 +10,7 @@
 import '@angular/localize/init';
 import {registerLocaleData} from '@angular/common';
 import localeRo from '@angular/common/locales/ro';
-import {Component, ContentChild, ContentChildren, Directive, HostBinding, Input, LOCALE_ID, QueryList, TemplateRef, Type, ViewChild, ViewContainerRef, Pipe, PipeTransform} from '@angular/core';
+import {Component, ContentChild, ContentChildren, Directive, HostBinding, Input, LOCALE_ID, QueryList, TemplateRef, Type, ViewChild, ViewContainerRef, Pipe, PipeTransform, NO_ERRORS_SCHEMA} from '@angular/core';
 import {setDelayProjection} from '@angular/core/src/render3/instructions/projection';
 import {TestBed} from '@angular/core/testing';
 import {loadTranslations, clearTranslations} from '@angular/localize';
@@ -22,7 +22,13 @@ import {computeMsgId} from '@angular/compiler';
 
 onlyInIvy('Ivy i18n logic').describe('runtime i18n', () => {
   beforeEach(() => {
-    TestBed.configureTestingModule({declarations: [AppComp, DirectiveWithTplRef, UppercasePipe]});
+    TestBed.configureTestingModule({
+      declarations: [AppComp, DirectiveWithTplRef, UppercasePipe],
+      // In some of the tests we use made-up tag names for better readability, however they'll
+      // cause validation errors. Add the `NO_ERRORS_SCHEMA` so that we don't have to declare
+      // dummy components for each one of them.
+      schemas: [NO_ERRORS_SCHEMA],
+    });
   });
 
   afterEach(() => {
diff --git a/packages/core/test/acceptance/ng_module_spec.ts b/packages/core/test/acceptance/ng_module_spec.ts
index 4258f09edbb89..09c4c96cff276 100644
--- a/packages/core/test/acceptance/ng_module_spec.ts
+++ b/packages/core/test/acceptance/ng_module_spec.ts
@@ -7,7 +7,7 @@
  */
 
 import {CommonModule} from '@angular/common';
-import {Component, NO_ERRORS_SCHEMA, NgModule} from '@angular/core';
+import {CUSTOM_ELEMENTS_SCHEMA, Component, NO_ERRORS_SCHEMA, NgModule} from '@angular/core';
 import {TestBed} from '@angular/core/testing';
 import {modifiedInIvy, onlyInIvy} from '@angular/private/testing';
 
@@ -164,6 +164,86 @@ describe('NgModule', () => {
         fixture.detectChanges();
       }).not.toThrow();
     });
-  });
 
+    it('should throw unknown element error without CUSTOM_ELEMENTS_SCHEMA for element with dash in tag name',
+       () => {
+         @Component({template: `<custom-el></custom-el>`})
+         class MyComp {
+         }
+
+         TestBed.configureTestingModule({declarations: [MyComp]});
+
+         expect(() => {
+           const fixture = TestBed.createComponent(MyComp);
+           fixture.detectChanges();
+         }).toThrowError(/'custom-el' is not a known element/);
+       });
+
+    it('should throw unknown element error without CUSTOM_ELEMENTS_SCHEMA for element without dash in tag name',
+       () => {
+         @Component({template: `<custom></custom>`})
+         class MyComp {
+         }
+
+         TestBed.configureTestingModule({declarations: [MyComp]});
+
+         expect(() => {
+           const fixture = TestBed.createComponent(MyComp);
+           fixture.detectChanges();
+         }).toThrowError(/'custom' is not a known element/);
+       });
+
+    it('should not throw unknown element error with CUSTOM_ELEMENTS_SCHEMA', () => {
+      @Component({template: `<custom-el></custom-el>`})
+      class MyComp {
+      }
+
+      TestBed.configureTestingModule({
+        declarations: [MyComp],
+        schemas: [CUSTOM_ELEMENTS_SCHEMA],
+      });
+
+      expect(() => {
+        const fixture = TestBed.createComponent(MyComp);
+        fixture.detectChanges();
+      }).not.toThrow();
+    });
+
+    it('should not throw unknown element error with NO_ERRORS_SCHEMA', () => {
+      @Component({template: `<custom-el></custom-el>`})
+      class MyComp {
+      }
+
+      TestBed.configureTestingModule({
+        declarations: [MyComp],
+        schemas: [NO_ERRORS_SCHEMA],
+      });
+
+      expect(() => {
+        const fixture = TestBed.createComponent(MyComp);
+        fixture.detectChanges();
+      }).not.toThrow();
+    });
+
+    it('should not throw unknown element error if element matches a directive', () => {
+      @Component({
+        selector: 'custom-el',
+        template: '',
+      })
+      class CustomEl {
+      }
+
+      @Component({template: `<custom-el></custom-el>`})
+      class MyComp {
+      }
+
+      TestBed.configureTestingModule({declarations: [MyComp, CustomEl]});
+
+      expect(() => {
+        const fixture = TestBed.createComponent(MyComp);
+        fixture.detectChanges();
+      }).not.toThrow();
+    });
+
+  });
 });
diff --git a/packages/core/test/linker/ng_module_integration_spec.ts b/packages/core/test/linker/ng_module_integration_spec.ts
index beef110c3a5fb..bdc52b9621fae 100644
--- a/packages/core/test/linker/ng_module_integration_spec.ts
+++ b/packages/core/test/linker/ng_module_integration_spec.ts
@@ -252,7 +252,7 @@ function declareTests(config?: {useJit: boolean}) {
 
       onlyInIvy('Unknown property warning logged, instead of throwing an error')
           .it('should error on unknown bound properties on custom elements by default', () => {
-            @Component({template: '<some-element [someUnknownProp]="true"></some-element>'})
+            @Component({template: '<div [someUnknownProp]="true"></div>'})
             class ComponentUsingInvalidProperty {
             }
 
diff --git a/packages/platform-browser/test/testing_public_spec.ts b/packages/platform-browser/test/testing_public_spec.ts
index c5f97a861c0a4..24608a88bdef6 100644
--- a/packages/platform-browser/test/testing_public_spec.ts
+++ b/packages/platform-browser/test/testing_public_spec.ts
@@ -958,7 +958,7 @@ Did you run and wait for 'resolveComponentResources()'?` :
 
       onlyInIvy(`Unknown property warning logged instead of an error`)
           .it('should error on unknown bound properties on custom elements by default', () => {
-            @Component({template: '<some-element [someUnknownProp]="true"></some-element>'})
+            @Component({template: '<div [someUnknownProp]="true"></div>'})
             class ComponentUsingInvalidProperty {
             }