diff --git a/README.md b/README.md
index fb14b5a8ce..f370a0151a 100644
--- a/README.md
+++ b/README.md
@@ -144,6 +144,7 @@ require("babylon").parse("code", {
  - `numericSeparator` ([proposal](https://github.com/samuelgoto/proposal-numeric-separator))
  - `optionalChaining` ([proposal](https://github.com/tc39/proposal-optional-chaining))
  - `importMeta` ([proposal](https://github.com/tc39/proposal-import-meta))
+ - `bigInt` ([proposal](https://github.com/tc39/proposal-bigint))
 
 ### FAQ
 
diff --git a/src/parser/expression.js b/src/parser/expression.js
index 588c1b106d..f044c613b4 100644
--- a/src/parser/expression.js
+++ b/src/parser/expression.js
@@ -554,6 +554,9 @@ export default class ExpressionParser extends LValParser {
       case tt.num:
         return this.parseLiteral(this.state.value, "NumericLiteral");
 
+      case tt.bigint:
+        return this.parseLiteral(this.state.value, "BigIntLiteral");
+
       case tt.string:
         return this.parseLiteral(this.state.value, "StringLiteral");
 
diff --git a/src/tokenizer/index.js b/src/tokenizer/index.js
index dca36f2175..d95d79d703 100644
--- a/src/tokenizer/index.js
+++ b/src/tokenizer/index.js
@@ -631,10 +631,27 @@ export default class Tokenizer extends LocationParser {
   }
 
   readRadixNumber(radix: number): void {
+    const start = this.state.pos;
+    let isBigInt = false;
+
     this.state.pos += 2; // 0x
     const val = this.readInt(radix);
     if (val == null) this.raise(this.state.start + 2, "Expected number in radix " + radix);
+
+    if (this.hasPlugin("bigInt")) {
+      if (this.input.charCodeAt(this.state.pos) === 0x6E) { // 'n'
+        ++this.state.pos;
+        isBigInt = true;
+      }
+    }
+
     if (isIdentifierStart(this.fullCharCodeAtPos())) this.raise(this.state.pos, "Identifier directly after number");
+
+    if (isBigInt) {
+      const str = this.input.slice(start, this.state.pos).replace(/[_n]/g, "");
+      return this.finishToken(tt.bigint, str);
+    }
+
     return this.finishToken(tt.num, val);
   }
 
@@ -642,30 +659,47 @@ export default class Tokenizer extends LocationParser {
 
   readNumber(startsWithDot: boolean): void {
     const start = this.state.pos;
-    let octal = this.input.charCodeAt(start) === 48; // '0'
+    let octal = this.input.charCodeAt(start) === 0x30; // '0'
     let isFloat = false;
+    let isBigInt = false;
 
     if (!startsWithDot && this.readInt(10) === null) this.raise(start, "Invalid number");
     if (octal && this.state.pos == start + 1) octal = false; // number === 0
 
     let next = this.input.charCodeAt(this.state.pos);
-    if (next === 46 && !octal) { // '.'
+    if (next === 0x2E && !octal) { // '.'
       ++this.state.pos;
       this.readInt(10);
       isFloat = true;
       next = this.input.charCodeAt(this.state.pos);
     }
 
-    if ((next === 69 || next === 101) && !octal) { // 'eE'
+    if ((next === 0x45 || next === 0x65) && !octal) { // 'Ee'
       next = this.input.charCodeAt(++this.state.pos);
-      if (next === 43 || next === 45) ++this.state.pos; // '+-'
+      if (next === 0x2B || next === 0x2D) ++this.state.pos; // '+-'
       if (this.readInt(10) === null) this.raise(start, "Invalid number");
       isFloat = true;
+      next = this.input.charCodeAt(this.state.pos);
+    }
+
+    if (this.hasPlugin("bigInt")) {
+      if (next === 0x6E) { // 'n'
+        // disallow floats and legacy octal syntax, new style octal ("0o") is handled in this.readRadixNumber
+        if (isFloat || octal) this.raise(start, "Invalid BigIntLiteral");
+        ++this.state.pos;
+        isBigInt = true;
+      }
     }
 
     if (isIdentifierStart(this.fullCharCodeAtPos())) this.raise(this.state.pos, "Identifier directly after number");
 
-    const str = this.input.slice(start, this.state.pos).replace(/_/g, "");
+    // remove "_" for numeric literal separator, and "n" for BigInts
+    const str = this.input.slice(start, this.state.pos).replace(/[_n]/g, "");
+
+    if (isBigInt) {
+      return this.finishToken(tt.bigint, str);
+    }
+
     let val;
     if (isFloat) {
       val = parseFloat(str);
diff --git a/src/tokenizer/types.js b/src/tokenizer/types.js
index 12d7ee1e93..89759681ed 100644
--- a/src/tokenizer/types.js
+++ b/src/tokenizer/types.js
@@ -82,6 +82,7 @@ export class BinopTokenType extends TokenType {
 
 export const types: { [name: string]: TokenType } = {
   num: new TokenType("num", { startsExpr }),
+  bigint: new TokenType("bigint", { startsExpr }),
   regexp: new TokenType("regexp", { startsExpr }),
   string: new TokenType("string", { startsExpr }),
   name: new TokenType("name", { startsExpr }),
diff --git a/src/types.js b/src/types.js
index d4c1041ae8..3a4acfaa08 100644
--- a/src/types.js
+++ b/src/types.js
@@ -96,6 +96,11 @@ export type NumericLiteral = NodeBase & {
   value: number;
 };
 
+export type BigIntLiteral = NodeBase & {
+  type: "BigIntLiteral";
+  value: number;
+}
+
 // Programs
 
 export type BlockStatementLike = Program | BlockStatement;
diff --git a/test/fixtures/experimental/bigint/invalid-decimal/actual.js b/test/fixtures/experimental/bigint/invalid-decimal/actual.js
new file mode 100644
index 0000000000..d87b390c40
--- /dev/null
+++ b/test/fixtures/experimental/bigint/invalid-decimal/actual.js
@@ -0,0 +1 @@
+1.0n
diff --git a/test/fixtures/experimental/bigint/invalid-decimal/options.json b/test/fixtures/experimental/bigint/invalid-decimal/options.json
new file mode 100644
index 0000000000..a1fd77a334
--- /dev/null
+++ b/test/fixtures/experimental/bigint/invalid-decimal/options.json
@@ -0,0 +1 @@
+{ "throws": "Invalid BigIntLiteral (1:0)" }
diff --git a/test/fixtures/experimental/bigint/invalid-e/actual.js b/test/fixtures/experimental/bigint/invalid-e/actual.js
new file mode 100644
index 0000000000..3bc83e85c1
--- /dev/null
+++ b/test/fixtures/experimental/bigint/invalid-e/actual.js
@@ -0,0 +1 @@
+2e9n
diff --git a/test/fixtures/experimental/bigint/invalid-e/options.json b/test/fixtures/experimental/bigint/invalid-e/options.json
new file mode 100644
index 0000000000..a1fd77a334
--- /dev/null
+++ b/test/fixtures/experimental/bigint/invalid-e/options.json
@@ -0,0 +1 @@
+{ "throws": "Invalid BigIntLiteral (1:0)" }
diff --git a/test/fixtures/experimental/bigint/invalid-octal-legacy/actual.js b/test/fixtures/experimental/bigint/invalid-octal-legacy/actual.js
new file mode 100644
index 0000000000..59dd202a6f
--- /dev/null
+++ b/test/fixtures/experimental/bigint/invalid-octal-legacy/actual.js
@@ -0,0 +1 @@
+016432n
diff --git a/test/fixtures/experimental/bigint/invalid-octal-legacy/options.json b/test/fixtures/experimental/bigint/invalid-octal-legacy/options.json
new file mode 100644
index 0000000000..a1fd77a334
--- /dev/null
+++ b/test/fixtures/experimental/bigint/invalid-octal-legacy/options.json
@@ -0,0 +1 @@
+{ "throws": "Invalid BigIntLiteral (1:0)" }
diff --git a/test/fixtures/experimental/bigint/options.json b/test/fixtures/experimental/bigint/options.json
new file mode 100644
index 0000000000..f6a5fb21f1
--- /dev/null
+++ b/test/fixtures/experimental/bigint/options.json
@@ -0,0 +1,3 @@
+{
+  "plugins": ["bigInt"]
+}
diff --git a/test/fixtures/experimental/bigint/valid-binary/actual.js b/test/fixtures/experimental/bigint/valid-binary/actual.js
new file mode 100644
index 0000000000..a61408b28a
--- /dev/null
+++ b/test/fixtures/experimental/bigint/valid-binary/actual.js
@@ -0,0 +1 @@
+0b101011101n
diff --git a/test/fixtures/experimental/bigint/valid-binary/expected.json b/test/fixtures/experimental/bigint/valid-binary/expected.json
new file mode 100644
index 0000000000..263ef53fc6
--- /dev/null
+++ b/test/fixtures/experimental/bigint/valid-binary/expected.json
@@ -0,0 +1,69 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 12,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 1,
+      "column": 12
+    }
+  },
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 12,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 1,
+        "column": 12
+      }
+    },
+    "sourceType": "script",
+    "body": [
+      {
+        "type": "ExpressionStatement",
+        "start": 0,
+        "end": 12,
+        "loc": {
+          "start": {
+            "line": 1,
+            "column": 0
+          },
+          "end": {
+            "line": 1,
+            "column": 12
+          }
+        },
+        "expression": {
+          "type": "BigIntLiteral",
+          "start": 0,
+          "end": 12,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 0
+            },
+            "end": {
+              "line": 1,
+              "column": 12
+            }
+          },
+          "extra": {
+            "rawValue": "0b101011101",
+            "raw": "0b101011101n"
+          },
+          "value": "0b101011101"
+        }
+      }
+    ],
+    "directives": []
+  }
+}
\ No newline at end of file
diff --git a/test/fixtures/experimental/bigint/valid-hex/actual.js b/test/fixtures/experimental/bigint/valid-hex/actual.js
new file mode 100644
index 0000000000..b5fa6179c8
--- /dev/null
+++ b/test/fixtures/experimental/bigint/valid-hex/actual.js
@@ -0,0 +1 @@
+0xFFF123n
diff --git a/test/fixtures/experimental/bigint/valid-hex/expected.json b/test/fixtures/experimental/bigint/valid-hex/expected.json
new file mode 100644
index 0000000000..64fe81e542
--- /dev/null
+++ b/test/fixtures/experimental/bigint/valid-hex/expected.json
@@ -0,0 +1,69 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 9,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 1,
+      "column": 9
+    }
+  },
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 9,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 1,
+        "column": 9
+      }
+    },
+    "sourceType": "script",
+    "body": [
+      {
+        "type": "ExpressionStatement",
+        "start": 0,
+        "end": 9,
+        "loc": {
+          "start": {
+            "line": 1,
+            "column": 0
+          },
+          "end": {
+            "line": 1,
+            "column": 9
+          }
+        },
+        "expression": {
+          "type": "BigIntLiteral",
+          "start": 0,
+          "end": 9,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 0
+            },
+            "end": {
+              "line": 1,
+              "column": 9
+            }
+          },
+          "extra": {
+            "rawValue": "0xFFF123",
+            "raw": "0xFFF123n"
+          },
+          "value": "0xFFF123"
+        }
+      }
+    ],
+    "directives": []
+  }
+}
\ No newline at end of file
diff --git a/test/fixtures/experimental/bigint/valid-large/actual.js b/test/fixtures/experimental/bigint/valid-large/actual.js
new file mode 100644
index 0000000000..bff78974b7
--- /dev/null
+++ b/test/fixtures/experimental/bigint/valid-large/actual.js
@@ -0,0 +1 @@
+9223372036854775807n
diff --git a/test/fixtures/experimental/bigint/valid-large/expected.json b/test/fixtures/experimental/bigint/valid-large/expected.json
new file mode 100644
index 0000000000..1536e3c7ae
--- /dev/null
+++ b/test/fixtures/experimental/bigint/valid-large/expected.json
@@ -0,0 +1,69 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 20,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 1,
+      "column": 20
+    }
+  },
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 20,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 1,
+        "column": 20
+      }
+    },
+    "sourceType": "script",
+    "body": [
+      {
+        "type": "ExpressionStatement",
+        "start": 0,
+        "end": 20,
+        "loc": {
+          "start": {
+            "line": 1,
+            "column": 0
+          },
+          "end": {
+            "line": 1,
+            "column": 20
+          }
+        },
+        "expression": {
+          "type": "BigIntLiteral",
+          "start": 0,
+          "end": 20,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 0
+            },
+            "end": {
+              "line": 1,
+              "column": 20
+            }
+          },
+          "extra": {
+            "rawValue": "9223372036854775807",
+            "raw": "9223372036854775807n"
+          },
+          "value": "9223372036854775807"
+        }
+      }
+    ],
+    "directives": []
+  }
+}
diff --git a/test/fixtures/experimental/bigint/valid-octal-new/actual.js b/test/fixtures/experimental/bigint/valid-octal-new/actual.js
new file mode 100644
index 0000000000..21e50f9aba
--- /dev/null
+++ b/test/fixtures/experimental/bigint/valid-octal-new/actual.js
@@ -0,0 +1 @@
+0o16432n
diff --git a/test/fixtures/experimental/bigint/valid-octal-new/expected.json b/test/fixtures/experimental/bigint/valid-octal-new/expected.json
new file mode 100644
index 0000000000..93103a5656
--- /dev/null
+++ b/test/fixtures/experimental/bigint/valid-octal-new/expected.json
@@ -0,0 +1,69 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 8,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 1,
+      "column": 8
+    }
+  },
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 8,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 1,
+        "column": 8
+      }
+    },
+    "sourceType": "script",
+    "body": [
+      {
+        "type": "ExpressionStatement",
+        "start": 0,
+        "end": 8,
+        "loc": {
+          "start": {
+            "line": 1,
+            "column": 0
+          },
+          "end": {
+            "line": 1,
+            "column": 8
+          }
+        },
+        "expression": {
+          "type": "BigIntLiteral",
+          "start": 0,
+          "end": 8,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 0
+            },
+            "end": {
+              "line": 1,
+              "column": 8
+            }
+          },
+          "extra": {
+            "rawValue": "0o16432",
+            "raw": "0o16432n"
+          },
+          "value": "0o16432"
+        }
+      }
+    ],
+    "directives": []
+  }
+}
\ No newline at end of file
diff --git a/test/fixtures/experimental/bigint/valid-small/actual.js b/test/fixtures/experimental/bigint/valid-small/actual.js
new file mode 100644
index 0000000000..9ad48c1bff
--- /dev/null
+++ b/test/fixtures/experimental/bigint/valid-small/actual.js
@@ -0,0 +1 @@
+100n
diff --git a/test/fixtures/experimental/bigint/valid-small/expected.json b/test/fixtures/experimental/bigint/valid-small/expected.json
new file mode 100644
index 0000000000..736974a559
--- /dev/null
+++ b/test/fixtures/experimental/bigint/valid-small/expected.json
@@ -0,0 +1,69 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 4,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 1,
+      "column": 4
+    }
+  },
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 4,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 1,
+        "column": 4
+      }
+    },
+    "sourceType": "script",
+    "body": [
+      {
+        "type": "ExpressionStatement",
+        "start": 0,
+        "end": 4,
+        "loc": {
+          "start": {
+            "line": 1,
+            "column": 0
+          },
+          "end": {
+            "line": 1,
+            "column": 4
+          }
+        },
+        "expression": {
+          "type": "BigIntLiteral",
+          "start": 0,
+          "end": 4,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 0
+            },
+            "end": {
+              "line": 1,
+              "column": 4
+            }
+          },
+          "extra": {
+            "rawValue": "100",
+            "raw": "100n"
+          },
+          "value": "100"
+        }
+      }
+    ],
+    "directives": []
+  }
+}