diff --git a/demo/DemoApp.tsx b/demo/DemoApp.tsx
index f340785..53842a5 100644
--- a/demo/DemoApp.tsx
+++ b/demo/DemoApp.tsx
@@ -56,6 +56,7 @@ export function DemoApp()
 	const [datetime, setDatetime] = useState(null);
 
 	const [selected, setSelected] = useState(null);
+	const [anotherSelected, setAnotherSelected] = useState(null);
 
 	const [page, setPage] = useState(11);
 
@@ -176,6 +177,18 @@ export function DemoApp()
 				}} value={selected} onChange={setSelected} selectibleMaxCount={3} placeholder={"Simple test"}>
 					Simple select test
 				</Select>
+
+				<Select value={anotherSelected} onChange={setAnotherSelected} options={{
+					"test": "test",
+					"foo": "foo",
+					"bar": "bar",
+				}} required={true}>
+					At least one selected element
+				</Select>
+
+				<Buttons placement={"center"}>
+					<button>Validation test</button>
+				</Buttons>
 			</form>
 
 			<h2>HTML</h2>
diff --git a/index.ts b/index.ts
index 681f0ec..3ed05de 100644
--- a/index.ts
+++ b/index.ts
@@ -15,6 +15,7 @@ export * from "./src/Components/Dates/Datepicker";
 export * from "./src/Components/Floating/Float";
 export * from "./src/Components/Floating/Tooltip";
 export * from "./src/Components/Forms/Checkbox";
+export * from "./src/Components/Forms/CustomValidationRule";
 export * from "./src/Components/Forms/DatepickerInput";
 export * from "./src/Components/Forms/PasswordInput";
 export * from "./src/Components/Forms/Radio";
diff --git a/package.json b/package.json
index 0951e39..d935e29 100644
--- a/package.json
+++ b/package.json
@@ -1,5 +1,5 @@
 {
-	"version": "1.4.2",
+	"version": "1.5.0",
 	"name": "@kernelui/core",
 	"description": "Kernel UI Core.",
 	"scripts": {
diff --git a/src/Components/Forms/CustomValidationRule.tsx b/src/Components/Forms/CustomValidationRule.tsx
new file mode 100644
index 0000000..47b6b38
--- /dev/null
+++ b/src/Components/Forms/CustomValidationRule.tsx
@@ -0,0 +1,24 @@
+import React, {useEffect, useRef} from "react";
+
+/**
+ * Custom validation rule in a form.
+ */
+export function CustomValidationRule({valid, errorMessage}: {
+	valid: boolean;
+	errorMessage: string;
+})
+{
+	// HTML virtual input ref.
+	const ref = useRef<HTMLInputElement>();
+
+	// When the validation is invalid, set a custom error message, set the custom error message.
+	useEffect(() => {
+		ref.current.setCustomValidity(valid ? "" : errorMessage);
+	}, [ref, valid, errorMessage]);
+
+	return (
+		<input ref={ref}
+		       className={"virtual"} type={"text"} required={true}
+		       value={valid ? "true" : ""} onChange={() => {}} />
+	);
+}
diff --git a/src/Components/Select/Select.tsx b/src/Components/Select/Select.tsx
index 20a2e66..b23b738 100644
--- a/src/Components/Select/Select.tsx
+++ b/src/Components/Select/Select.tsx
@@ -3,6 +3,7 @@ import {Suggestible} from "./Suggestible";
 import {OptionsSuggestions, useSuggestionsNavigation} from "./OptionsSuggestions";
 import {classes, Modify, normalizeString} from "../../Utils";
 import {CaretDown, Check, X} from "@phosphor-icons/react";
+import {CustomValidationRule} from "../Forms/CustomValidationRule";
 
 /**
  * Generic select component properties.
@@ -37,6 +38,12 @@ export type SelectProperties<OptionKey extends keyof any, Option> = React.PropsW
 	 */
 	match?: (search: string, option: Option) => boolean;
 
+	/**
+	 * Min count of options to allow to select.
+	 * 0 by default, 1 when required is true.
+	 */
+	selectibleMinCount?: number;
+
 	/**
 	 * Max count of options to allow to select.
 	 * 1 by default when multiple is false, infinity when multiple is true.
@@ -74,6 +81,7 @@ export function Select<OptionKey extends keyof any, Option>(
 		className,
 		value, onChange,
 		options, renderOption, match,
+		required, selectibleMinCount,
 		selectibleMaxCount, multiple,
 		blurOnSelect, blurWhenMaxCountSelected,
 		// Properties to pass down.
@@ -90,6 +98,10 @@ export function Select<OptionKey extends keyof any, Option>(
 	// If `multiple` is set and `selectibleMaxCount` is not, allow an infinite count of options to select.
 	selectibleMaxCount = selectibleMaxCount ?? ((multiple === undefined ? false : multiple) ? Infinity : 1);
 
+	// By default, allow to select no option.
+	// If `required` is set, `selectibleMinCount` will be set as 1 by default.
+	selectibleMinCount = selectibleMinCount ?? (required ? 1 : 0);
+
 	// true by default.
 	blurOnSelect = blurOnSelect === undefined ? false : blurOnSelect;
 	blurWhenMaxCountSelected = blurWhenMaxCountSelected === undefined ? true : blurWhenMaxCountSelected;
@@ -213,6 +225,9 @@ export function Select<OptionKey extends keyof any, Option>(
 				<a className={"button"} tabIndex={-1}><CaretDown /></a>
 			</div>
 
+			<CustomValidationRule valid={selectedOptions.length >= selectibleMinCount}
+			                      errorMessage={`At least ${selectibleMinCount} option${selectibleMinCount > 1 ? "s are" : " is"} required.`} />
+
 			<ul className={"selected"}>
 				{ // Showing each selected value.
 					selectedOptions.map(([optionKey, option]) => (
diff --git a/src/styles/_common.less b/src/styles/_common.less
index df3448c..6db24ac 100644
--- a/src/styles/_common.less
+++ b/src/styles/_common.less
@@ -27,3 +27,9 @@ p
 	margin: 0.75em auto;
 	line-height: 1.6em;
 }
+
+.virtual
+{
+	position: absolute;
+	opacity: 0;
+}