diff --git a/.changeset/gorgeous-numbers-hear.md b/.changeset/gorgeous-numbers-hear.md
new file mode 100644
index 0000000..41ca94a
--- /dev/null
+++ b/.changeset/gorgeous-numbers-hear.md
@@ -0,0 +1,5 @@
+---
+"enhanced-ms": minor
+---
+
+Add support for Polish, Czech, and Chinese (Simplified)
diff --git a/README.md b/README.md
index fdbaf57..e740fd8 100644
--- a/README.md
+++ b/README.md
@@ -50,16 +50,19 @@ As mentioned above, `enhanced-ms` is an enhanced version of the popular [`ms`](h
 
 The currently supported languages include:
 
-| Language          | Key |
-| ----------------- | --- |
-| English (default) | en  |
-| German            | de  |
-| Russian           | ru  |
-| Māori             | mi  |
-| Spanish           | es  |
-| Dutch             | nl  |
-| Italian           | it  |
-| French            | fr  |
+| Language              | Key   |
+| --------------------- | ----- |
+| English (default)     | en    |
+| German                | de    |
+| Russian               | ru    |
+| Māori                 | mi    |
+| Spanish               | es    |
+| Dutch                 | nl    |
+| Italian               | it    |
+| French                | fr    |
+| Czech                 | cs    |
+| Polish                | pl    |
+| Chinese (Simplified)  | zh-CN |
 
 You can help by adding support for more languages.
 
diff --git a/src/languages/cs.ts b/src/languages/cs.ts
new file mode 100644
index 0000000..6dbdf65
--- /dev/null
+++ b/src/languages/cs.ts
@@ -0,0 +1,100 @@
+type Unit = keyof typeof UnitsMap;
+const UnitsMap = {
+  nanosekundy: ['nanosekunda', 'nanosekundy', 'nanosekund'],
+  mikrosekundy: ['mikrosekunda', 'mikrosekundy', 'mikrosekund'],
+  milisekundy: ['milisekunda', 'milisekundy', 'milisekund'],
+  sekundy: ['sekunda', 'sekundy', 'sekund'],
+  minuty: ['minuta', 'minuty', 'minut'],
+  hodiny: ['hodina', 'hodiny', 'hodin'],
+  dny: ['den', 'dny', 'dní'],
+  týdny: ['týden', 'týdny', 'týdnů'],
+  měsíce: ['měsíc', 'měsíce', 'měsíců'],
+  roky: ['rok', 'roky', 'let'],
+  dekády: ['dekáda', 'dekády', 'dekád'],
+  století: ['století', 'století', 'století'],
+  tisíciletí: ['tisíciletí', 'tisíciletí', 'tisíciletí'],
+} as const;
+
+function formatTime(unit: Unit, count: number) {
+  const words = UnitsMap[unit];
+
+  let word: string;
+  if (count === 1) word = words[0]!;
+  else if (count >= 2 && count <= 4) word = words[1]!;
+  else word = words[2]!;
+
+  return word || '';
+}
+
+export default {
+  decimal: ',',
+  and: 'a',
+
+  units: {
+    nanosecond: {
+      name: (c) => formatTime('nanosekundy', c),
+      abbreviation: 'ns',
+      matches: ['ns', 'nanosekunda', 'nanosekundy', 'nanosekund'],
+    },
+    microsecond: {
+      name: (c) => formatTime('mikrosekundy', c),
+      abbreviation: 'μs',
+      matches: ['μs', 'us', 'mikrosekunda', 'mikrosekundy', 'mikrosekund'],
+    },
+    millisecond: {
+      name: (c) => formatTime('milisekundy', c),
+      abbreviation: 'ms',
+      matches: ['ms', 'milisekunda', 'milisekundy', 'milisekund'],
+    },
+    second: {
+      name: (c) => formatTime('sekundy', c),
+      abbreviation: 's',
+      matches: ['s', 'sek', 'sekunda', 'sekundy', 'sekund'],
+    },
+    minute: {
+      name: (c) => formatTime('minuty', c),
+      abbreviation: 'min',
+      matches: ['m', 'min', 'minuta', 'minuty', 'minut'],
+    },
+    hour: {
+      name: (c) => formatTime('hodiny', c),
+      abbreviation: 'h',
+      matches: ['h', 'hod', 'hodina', 'hodiny', 'hodin'],
+    },
+    day: {
+      name: (c) => formatTime('dny', c),
+      abbreviation: 'd',
+      matches: ['d', 'den', 'dny', 'dní'],
+    },
+    week: {
+      name: (c) => formatTime('týdny', c),
+      abbreviation: 'týd.',
+      matches: ['w', 'týd', 'týden', 'týdny', 'týdnů'],
+    },
+    month: {
+      name: (c) => formatTime('měsíce', c),
+      abbreviation: 'měs.',
+      matches: ['mo', 'měs', 'měsíc', 'měsíce', 'měsíců'],
+    },
+    year: {
+      name: (c) => formatTime('roky', c),
+      abbreviation: 'r.',
+      matches: ['y', 'r', 'rok', 'roky', 'let'],
+    },
+    decade: {
+      name: (c) => formatTime('dekády', c),
+      abbreviation: 'dek.',
+      matches: ['dek', 'dekáda', 'dekády', 'dekád'],
+    },
+    century: {
+      name: (c) => formatTime('století', c),
+      abbreviation: 'stol.',
+      matches: ['c', 'stol', 'století'],
+    },
+    millennium: {
+      name: (c) => formatTime('tisíciletí', c),
+      abbreviation: 'tis.',
+      matches: ['mil', 'tis', 'tisíciletí'],
+    },
+  },
+} satisfies import('./helpers/definition-types').LanguageDefinition;
diff --git a/src/languages/index.ts b/src/languages/index.ts
index 3018c0c..1e6c73b 100644
--- a/src/languages/index.ts
+++ b/src/languages/index.ts
@@ -1,5 +1,6 @@
 import type { LanguageDefinition } from './helpers/definition-types';
 
+import cs from './cs';
 import de from './de';
 import en from './en';
 import es from './es';
@@ -7,9 +8,34 @@ import fr from './fr';
 import it from './it';
 import mi from './mi';
 import nl from './nl';
+import pl from './pl';
 import ru from './ru';
+import zhCN from './zh-CN';
 
 // This prevents the whole language definition being included in the dts output
-type Locale = 'de' | 'en' | 'es' | 'fr' | 'it' | 'mi' | 'nl' | 'ru';
+type Locale =
+  | 'cs'
+  | 'de'
+  | 'en'
+  | 'es'
+  | 'fr'
+  | 'it'
+  | 'mi'
+  | 'nl'
+  | 'pl'
+  | 'ru'
+  | 'zh-CN';
 type Languages = Record<Locale, LanguageDefinition>;
-export const languages: Languages = { de, en, es, fr, it, mi, nl, ru };
+export const languages: Languages = {
+  cs,
+  de,
+  en,
+  es,
+  fr,
+  it,
+  mi,
+  nl,
+  pl,
+  ru,
+  'zh-CN': zhCN,
+};
diff --git a/src/languages/pl.ts b/src/languages/pl.ts
new file mode 100644
index 0000000..70a71ec
--- /dev/null
+++ b/src/languages/pl.ts
@@ -0,0 +1,104 @@
+type Unit = keyof typeof UnitsMap;
+const UnitsMap = {
+  nanosekundy: ['nanosekunda', 'nanosekundy', 'nanosekund'],
+  mikrosekundy: ['mikrosekunda', 'mikrosekundy', 'mikrosekund'],
+  milisekundy: ['milisekunda', 'milisekundy', 'milisekund'],
+  sekundy: ['sekunda', 'sekundy', 'sekund'],
+  minuty: ['minuta', 'minuty', 'minut'],
+  godziny: ['godzina', 'godziny', 'godzin'],
+  dni: ['dzień', 'dni', 'dni'],
+  tygodnie: ['tydzień', 'tygodnie', 'tygodni'],
+  miesiące: ['miesiąc', 'miesiące', 'miesięcy'],
+  lata: ['rok', 'lata', 'lat'],
+  dekady: ['dekada', 'dekady', 'dekad'],
+  wieki: ['wiek', 'wieki', 'wieków'],
+  tysiąclecia: ['tysiąclecie', 'tysiąclecia', 'tysiącleci'],
+} as const;
+
+function formatTime(unit: Unit, count: number) {
+  const words = UnitsMap[unit];
+
+  const lastDigit = count % 10;
+  const lastTwoDigits = count % 100;
+
+  let word: string;
+  if (lastTwoDigits >= 11 && lastTwoDigits <= 19) word = words[2]!;
+  else if (lastDigit === 1) word = words[0]!;
+  else if (lastDigit >= 2 && lastDigit <= 4) word = words[1]!;
+  else word = words[2]!;
+
+  return word || '';
+}
+
+export default {
+  decimal: ',',
+  and: 'i',
+
+  units: {
+    nanosecond: {
+      name: (c) => formatTime('nanosekundy', c),
+      abbreviation: 'ns',
+      matches: ['ns', 'nanosekunda', 'nanosekundy', 'nanosekund'],
+    },
+    microsecond: {
+      name: (c) => formatTime('mikrosekundy', c),
+      abbreviation: 'μs',
+      matches: ['μs', 'us', 'mikrosekunda', 'mikrosekundy', 'mikrosekund'],
+    },
+    millisecond: {
+      name: (c) => formatTime('milisekundy', c),
+      abbreviation: 'ms',
+      matches: ['ms', 'milisekunda', 'milisekundy', 'milisekund'],
+    },
+    second: {
+      name: (c) => formatTime('sekundy', c),
+      abbreviation: 's',
+      matches: ['s', 'sek', 'sekunda', 'sekundy', 'sekund'],
+    },
+    minute: {
+      name: (c) => formatTime('minuty', c),
+      abbreviation: 'min',
+      matches: ['m', 'min', 'minuta', 'minuty', 'minut'],
+    },
+    hour: {
+      name: (c) => formatTime('godziny', c),
+      abbreviation: 'godz.',
+      matches: ['h', 'godz', 'godzina', 'godziny', 'godzin'],
+    },
+    day: {
+      name: (c) => formatTime('dni', c),
+      abbreviation: 'd',
+      matches: ['d', 'dzień', 'dni'],
+    },
+    week: {
+      name: (c) => formatTime('tygodnie', c),
+      abbreviation: 'tydz.',
+      matches: ['w', 'tydz', 'tydzień', 'tygodnie', 'tygodni'],
+    },
+    month: {
+      name: (c) => formatTime('miesiące', c),
+      abbreviation: 'mies.',
+      matches: ['mo', 'mies', 'miesiąc', 'miesiące', 'miesięcy'],
+    },
+    year: {
+      name: (c) => formatTime('lata', c),
+      abbreviation: 'r.',
+      matches: ['y', 'r', 'rok', 'lata', 'lat'],
+    },
+    decade: {
+      name: (c) => formatTime('dekady', c),
+      abbreviation: 'dek.',
+      matches: ['dek', 'dekada', 'dekady', 'dekad'],
+    },
+    century: {
+      name: (c) => formatTime('wieki', c),
+      abbreviation: 'w.',
+      matches: ['c', 'wiek', 'wieki', 'wieków'],
+    },
+    millennium: {
+      name: (c) => formatTime('tysiąclecia', c),
+      abbreviation: 'tys.',
+      matches: ['mil', 'tys', 'tysiąclecie', 'tysiąclecia', 'tysiącleci'],
+    },
+  },
+} satisfies import('./helpers/definition-types').LanguageDefinition;
diff --git a/src/languages/zh-CN.ts b/src/languages/zh-CN.ts
new file mode 100644
index 0000000..4dafa15
--- /dev/null
+++ b/src/languages/zh-CN.ts
@@ -0,0 +1,71 @@
+export default {
+  decimal: '.',
+  and: '和',
+  units: {
+    nanosecond: {
+      name: '纳秒',
+      abbreviation: 'ns',
+      matches: ['纳秒', 'ns'],
+    },
+    microsecond: {
+      name: '微秒',
+      abbreviation: 'μs',
+      matches: ['微秒', 'μs', 'us'],
+    },
+    millisecond: {
+      name: '毫秒',
+      abbreviation: 'ms',
+      matches: ['毫秒', 'ms'],
+    },
+    second: {
+      name: '秒',
+      abbreviation: 's',
+      matches: ['秒', 's'],
+    },
+    minute: {
+      name: '分钟',
+      abbreviation: '分',
+      matches: ['分钟', '分', 'm', 'min'],
+    },
+    hour: {
+      name: '小时',
+      abbreviation: '时',
+      matches: ['小时', '时', 'h', 'hour'],
+    },
+    day: {
+      name: '天',
+      abbreviation: '天',
+      matches: ['天', '日', 'd', 'day'],
+    },
+    week: {
+      name: '周',
+      abbreviation: '周',
+      matches: ['周', '星期', 'w', 'week'],
+    },
+    month: {
+      name: '个月',
+      abbreviation: '月',
+      matches: ['个月', '月', 'mo', 'month'],
+    },
+    year: {
+      name: '年',
+      abbreviation: '年',
+      matches: ['年', 'y', 'year'],
+    },
+    decade: {
+      name: '十年',
+      abbreviation: '十年',
+      matches: ['十年', 'dec', 'decade'],
+    },
+    century: {
+      name: '世纪',
+      abbreviation: '世纪',
+      matches: ['世纪', 'c', 'century'],
+    },
+    millennium: {
+      name: '千年',
+      abbreviation: '千年',
+      matches: ['千年', 'mil', 'millennium'],
+    },
+  },
+} satisfies import('./helpers/definition-types').LanguageDefinition;
diff --git a/tests/cs.test.ts b/tests/cs.test.ts
new file mode 100644
index 0000000..8ff06b3
--- /dev/null
+++ b/tests/cs.test.ts
@@ -0,0 +1,34 @@
+import { createMs } from 'enhanced-ms';
+import { describe, expect, it } from 'vitest';
+
+const ms = createMs({ language: 'cs' });
+
+describe('Czech (Čeština)', () => {
+  describe('format milliseconds', () => {
+    it('formats with correct pluralization', () => {
+      // 1 second -> sekunda
+      expect(ms(1000)).toBe('1 sekunda');
+      // 2 seconds -> sekundy
+      expect(ms(2000)).toBe('2 sekundy');
+      // 4 seconds -> sekundy
+      expect(ms(4000)).toBe('4 sekundy');
+      // 5 seconds -> sekund
+      expect(ms(5000)).toBe('5 sekund');
+    });
+
+    it('formats with proper unit names', () => {
+      // 1 day 2 hours 5 minutes
+      const time = 86400000 + 2 * 3600000 + 5 * 60000;
+      expect(ms(time)).toBe('1 den 2 hodiny 5 minut');
+    });
+  });
+
+  describe('parse duration', () => {
+    it('parses Czech duration strings', () => {
+      expect(ms('1 sekunda')).toBe(1000);
+      expect(ms('2 sekundy')).toBe(2000);
+      expect(ms('5 sekund')).toBe(5000);
+      expect(ms('1 den 2 hodiny')).toBe(86400000 + 2 * 3600000);
+    });
+  });
+});
diff --git a/tests/pl.test.ts b/tests/pl.test.ts
new file mode 100644
index 0000000..518c1d4
--- /dev/null
+++ b/tests/pl.test.ts
@@ -0,0 +1,38 @@
+import { createMs } from 'enhanced-ms';
+import { describe, expect, it } from 'vitest';
+
+const ms = createMs({ language: 'pl' });
+
+describe('Polish (Polski)', () => {
+  describe('format milliseconds', () => {
+    it('formats with correct pluralization', () => {
+      // 1 second -> sekunda
+      expect(ms(1000)).toBe('1 sekunda');
+      // 2 seconds -> sekundy
+      expect(ms(2000)).toBe('2 sekundy');
+      // 5 seconds -> sekund
+      expect(ms(5000)).toBe('5 sekund');
+      // 12 seconds -> sekund (teen)
+      expect(ms(12000)).toBe('12 sekund');
+      // 22 seconds -> sekundy (ends in 2 but not teen)
+      expect(ms(22000)).toBe('22 sekundy');
+      // 25 seconds -> sekund
+      expect(ms(25000)).toBe('25 sekund');
+    });
+
+    it('formats with proper unit names', () => {
+      // 1 day 2 hours 5 minutes
+      const time = 86400000 + 2 * 3600000 + 5 * 60000;
+      expect(ms(time)).toBe('1 dzień 2 godziny 5 minut');
+    });
+  });
+
+  describe('parse duration', () => {
+    it('parses Polish duration strings', () => {
+      expect(ms('1 sekunda')).toBe(1000);
+      expect(ms('2 sekundy')).toBe(2000);
+      expect(ms('5 sekund')).toBe(5000);
+      expect(ms('1 dzień 2 godziny')).toBe(86400000 + 2 * 3600000);
+    });
+  });
+});
diff --git a/tests/zh-CN.test.ts b/tests/zh-CN.test.ts
new file mode 100644
index 0000000..68994ce
--- /dev/null
+++ b/tests/zh-CN.test.ts
@@ -0,0 +1,33 @@
+import { createMs } from 'enhanced-ms';
+import { describe, expect, it } from 'vitest';
+
+const ms = createMs({ language: 'zh-CN' });
+
+describe('Chinese Simplified (中文简体)', () => {
+  describe('format milliseconds', () => {
+    it('formats seconds correctly', () => {
+      expect(ms(1000)).toBe('1 秒');
+      expect(ms(5000)).toBe('5 秒');
+    });
+
+    it('formats with proper unit names', () => {
+      // 1 day 2 hours 5 minutes
+      const time = 86400000 + 2 * 3600000 + 5 * 60000;
+      expect(ms(time)).toBe('1 天 2 小时 5 分钟');
+    });
+
+    it('formats hours and minutes', () => {
+      expect(ms(3600000)).toBe('1 小时');
+      expect(ms(60000)).toBe('1 分钟');
+      expect(ms(3660000)).toBe('1 小时 1 分钟');
+    });
+  });
+
+  describe('parse duration', () => {
+    it('parses Chinese duration strings', () => {
+      expect(ms('1 秒')).toBe(1000);
+      expect(ms('5 秒')).toBe(5000);
+      expect(ms('1 天 2 小时')).toBe(86400000 + 2 * 3600000);
+    });
+  });
+});