diff --git a/src/config-array.js b/src/config-array.js
index 846e226..eb5bb32 100644
--- a/src/config-array.js
+++ b/src/config-array.js
@@ -841,7 +841,9 @@ export class ConfigArray extends Array {
 
 		assertNormalized(this);
 
-		const relativeDirectoryPath = path.relative(this.basePath, directoryPath);
+		const relativeDirectoryPath = path.relative(this.basePath, directoryPath)
+			.replace(/\\/g, '/');
+
 		if (relativeDirectoryPath.startsWith('..')) {
 			return true;
 		}
@@ -852,14 +854,35 @@ export class ConfigArray extends Array {
 		if (cache.has(relativeDirectoryPath)) {
 			return cache.get(relativeDirectoryPath);
 		}
-		
-		// first check non-/** paths
-		const result = shouldIgnorePath(
-			this.ignores, //.filter(matcher => typeof matcher === "function" || !matcher.endsWith("/**")),
-			directoryPath,
-			relativeDirectoryPath
-		);
 
+		const directoryParts = relativeDirectoryPath.split('/');
+		let relativeDirectoryToCheck = '';
+		let result = false;
+
+		/*
+		 * In order to get the correct gitignore-style ignores, where an
+		 * ignored parent directory cannot have any descendants unignored,
+		 * we need to check every directory starting at the parent all
+		 * the way down to the actual requested directory.
+		 * 
+		 * We aggressively cache all of this info to make sure we don't
+		 * have to recalculate everything for every call.
+		 */
+		do {
+
+			relativeDirectoryToCheck += directoryParts.shift() + '/';
+
+			result = shouldIgnorePath(
+				this.ignores,
+				path.join(this.basePath, relativeDirectoryToCheck),
+				relativeDirectoryToCheck
+			);
+
+			cache.set(relativeDirectoryToCheck, result);
+
+		} while (!result && directoryParts.length);
+
+		// also cache the result for the requested path
 		cache.set(relativeDirectoryPath, result);
 
 		return result;
diff --git a/tests/config-array.test.js b/tests/config-array.test.js
index 7260a1f..62cbdc0 100644
--- a/tests/config-array.test.js
+++ b/tests/config-array.test.js
@@ -1007,7 +1007,7 @@ describe('ConfigArray', () => {
 				expect(configs.isFileIgnored(path.join(basePath, 'foo/bar/a.js'))).to.be.true;
 			});
 
-			it('should return false when an ignored directory is later unignored with **', () => {
+			it('should return true when an ignored directory is later negated with **', () => {
 				configs = new ConfigArray([
 					{
 						files: ['**/*.js']
@@ -1028,10 +1028,10 @@ describe('ConfigArray', () => {
 
 				configs.normalizeSync();
 
-				expect(configs.isFileIgnored(path.join(basePath, 'node_modules/package/a.js'))).to.be.false;
+				expect(configs.isFileIgnored(path.join(basePath, 'node_modules/package/a.js'))).to.be.true;
 			});
 
-			it('should return false when an ignored directory is later unignored with *', () => {
+			it('should return true when an ignored directory is later negated with *', () => {
 				configs = new ConfigArray([
 					{
 						files: ['**/*.js']
@@ -1052,7 +1052,7 @@ describe('ConfigArray', () => {
 
 				configs.normalizeSync();
 
-				expect(configs.isFileIgnored(path.join(basePath, 'node_modules/package/a.js'))).to.be.false;
+				expect(configs.isFileIgnored(path.join(basePath, 'node_modules/package/a.js'))).to.be.true;
 			});
 
 			it('should return true when there are only patterns ending with /*', () => {
@@ -1216,7 +1216,7 @@ describe('ConfigArray', () => {
 				expect(configs.isDirectoryIgnored(path.join(basePath, 'node_modules') + '/'), 'Trailing slash').to.be.true;
 			});
 
-			it('should return false when a directory followed by ** is in ignores', () => {
+			it('should return true when a directory followed by ** is in ignores', () => {
 				configs = new ConfigArray([
 					{
 						ignores: ['**/node_modules/**']
@@ -1227,8 +1227,8 @@ describe('ConfigArray', () => {
 
 				configs.normalizeSync();
 
-				expect(configs.isDirectoryIgnored(path.join(basePath, 'node_modules'))).to.be.false;
-				expect(configs.isDirectoryIgnored(path.join(basePath, 'node_modules') + '/')).to.be.false;
+				expect(configs.isDirectoryIgnored(path.join(basePath, 'node_modules'))).to.be.true;
+				expect(configs.isDirectoryIgnored(path.join(basePath, 'node_modules') + '/')).to.be.true;
 				
 			});
 
@@ -1361,7 +1361,7 @@ describe('ConfigArray', () => {
 			});
 
 
-			it('should return false when an ignored directory is later unignored with **', () => {
+			it('should return true when an ignored directory is later negated with **', () => {
 				configs = new ConfigArray([
 					{
 						files: ['**/*.js']
@@ -1382,11 +1382,11 @@ describe('ConfigArray', () => {
 
 				configs.normalizeSync();
 
-				expect(configs.isDirectoryIgnored(path.join(basePath, 'node_modules/package'))).to.be.false;
-				expect(configs.isDirectoryIgnored(path.join(basePath, 'node_modules/package/'))).to.be.false;
+				expect(configs.isDirectoryIgnored(path.join(basePath, 'node_modules/package'))).to.be.true;
+				expect(configs.isDirectoryIgnored(path.join(basePath, 'node_modules/package/'))).to.be.true;
 			});
 
-			it('should return false when an ignored directory is later unignored with *', () => {
+			it('should return true when an ignored directory is later unignored with *', () => {
 				configs = new ConfigArray([
 					{
 						files: ['**/*.js']
@@ -1407,10 +1407,77 @@ describe('ConfigArray', () => {
 
 				configs.normalizeSync();
 
-				expect(configs.isDirectoryIgnored(path.join(basePath, 'node_modules/package'))).to.be.false;
-				expect(configs.isDirectoryIgnored(path.join(basePath, 'node_modules/package/'))).to.be.false;
+				expect(configs.isDirectoryIgnored(path.join(basePath, 'node_modules/package'))).to.be.true;
+				expect(configs.isDirectoryIgnored(path.join(basePath, 'node_modules/package/'))).to.be.true;
 			});
 
+			// https://github.com/eslint/eslint/pull/16579/files
+			describe('gitignore-style unignores', () => {
+
+				it('should return false when first-level subdirectories are ignored and then one is negated', () => {
+					configs = new ConfigArray([
+						{
+							ignores: [
+								'**/node_modules/*',
+								'!**/node_modules/foo/'
+							],
+						}
+					], { basePath });
+
+					configs.normalizeSync();
+					const directoryPath = path.resolve(basePath, 'node_modules/foo');
+
+					expect(configs.isDirectoryIgnored(directoryPath)).to.be.false;
+				});
+
+				it('should return false when first-level subdirectories are ignored with leading slash and then one is negated', () => {
+					configs = new ConfigArray([
+						{
+							ignores: [
+								'/**/node_modules/*',
+								'!**/node_modules/foo/'
+							],
+						}
+					], { basePath });
+
+					configs.normalizeSync();
+					const directoryPath = path.resolve(basePath, 'node_modules/foo');
+
+					expect(configs.isDirectoryIgnored(directoryPath)).to.be.false;
+				});
+
+				it('should return true when all descendant subdirectories are ignored and then one is negated', () => {
+					configs = new ConfigArray([
+						{
+							ignores: [
+								'**/node_modules/**',
+								'!**/node_modules/foo/'
+							],
+						}
+					], { basePath });
+
+					configs.normalizeSync();
+					const directoryPath = path.resolve(basePath, 'node_modules/foo');
+
+					expect(configs.isDirectoryIgnored(directoryPath)).to.be.true;
+				});
+
+				it('should return true when all descendant subdirectories are ignored and then other descendants are negated', () => {
+					configs = new ConfigArray([
+						{
+							ignores: [
+								'**/node_modules/**',
+								'!**/node_modules/foo/**'
+							],
+						}
+					], { basePath });
+
+					configs.normalizeSync();
+					const directoryPath = path.resolve(basePath, 'node_modules/foo');
+
+					expect(configs.isDirectoryIgnored(directoryPath)).to.be.true;
+				});
+			});
 
 		});