diff --git a/Sources/AOC2018/day09.swift b/Sources/AOC2018/day09.swift
new file mode 100644
index 0000000..370dadb
--- /dev/null
+++ b/Sources/AOC2018/day09.swift
@@ -0,0 +1,187 @@
+//
+// Advent of Code 2018 "Day 9: Marble Mania"
+//
+
+import Foundation
+
+struct List {
+    var val = 0
+    var ptrNext = -1
+    var ptrPrev = -1
+}
+
+class Marble {
+    var player: [Int] = []
+    var lastMarble = 0
+    var circle: [List] = []
+    var circleCount = 1
+    var currentMarble = 0
+    var currentPlayer = 0
+    var PC = 0
+
+    init(numPlayers: Int, lastMarble last: Int) {
+        circle = Array(repeating: List(), count: last+1)
+        circleCount = 1
+        currentMarble = 0
+        currentPlayer = 0
+        PC = 0
+        circle[0].ptrNext = 0
+        circle[0].ptrPrev = 0
+
+        player = Array(repeating: 0, count: numPlayers)
+        for num in 0...last { circle[num].val = num }
+        lastMarble = last
+    }
+
+    func insert() {
+        circle[currentMarble].ptrNext = circle[PC].val
+        circle[currentMarble].ptrPrev = circle[PC].ptrPrev
+        circle[circle[PC].ptrPrev].ptrNext = circle[currentMarble].val
+        circle[PC].ptrPrev = circle[currentMarble].val
+        PC = currentMarble
+        circleCount += 1
+    }
+
+    func remove() {
+        circle[circle[PC].ptrPrev].ptrNext = circle[PC].ptrNext
+        circle[circle[PC].ptrNext].ptrPrev = circle[PC].ptrPrev
+        PC = circle[circle[PC].ptrPrev].ptrNext
+        circleCount -= 1
+    }
+
+    func incrPC() {
+        PC = circle[PC].ptrNext
+    }
+
+    func incrPC(by n: Int) {
+        for _ in 0..<n { incrPC() }
+    }
+
+    func decrPC() {
+        PC = circle[PC].ptrPrev
+    }
+
+    func decrPC(by n: Int) {
+        for _ in 0..<n { decrPC() }
+    }
+
+    func incrPlayer() {
+        currentPlayer += 1
+        if currentPlayer == player.count { currentPlayer = 0 }
+    }
+
+    func placeNextMarble() {
+        currentMarble += 1
+        if currentMarble % 23 == 0 {
+            player[currentPlayer] += currentMarble
+            decrPC(by: 7)
+            player[currentPlayer] += circle[PC].val
+            remove()
+        } else {
+            incrPC(by: 2)
+            insert()
+        }
+        incrPlayer()
+    }
+
+}
+
+class Day09: AOCDay {
+    lazy var tests: (() -> ()) = day09Tests
+    lazy var final: (() -> ()) = day09Final
+
+    let testData: [(Int, Int, Int)] = [
+        (9, 25, 32),
+        (13, 7999, 146373),
+        (17, 1104, 2764),
+        (21, 6111, 54718),
+        (30, 5807, 37305)
+    ]
+
+    let finalData = (477, 70851)
+
+    func printCircle(circle: [List], withCount circleCount: Int) -> String {
+        var retVal = ""
+        var marble = circle[0]
+        for _ in 0..<circleCount {
+            retVal += "\(marble.val), "
+            marble = circle[marble.ptrNext]
+        }
+        return retVal
+    }
+
+    func testMarbleInit() {
+        let marb = Marble(numPlayers: 9, lastMarble: 15)
+        let result = printCircle(circle: marb.circle, withCount: marb.circleCount)
+        XCTAssertEqual(test: "testMarbleInit num", withExpression: (marb.player.count == 9))
+        XCTAssertEqual(test: "testMarbleInit last", withExpression: (marb.lastMarble == 15))
+        XCTAssertEqual(test: "testMarbleInit result", withExpression: (result == "0, "))        
+    }
+
+    func testInsert() {
+        let marb = Marble(numPlayers: 9, lastMarble: 15)
+        for _ in 0...3 {
+            marb.currentMarble += 1
+            marb.insert()
+            marb.incrPC(by:2)
+        }
+        let result = printCircle(circle: marb.circle, withCount: marb.circleCount)
+        XCTAssertEqual(test: "testInsert result", withExpression: (result == "0, 4, 2, 1, 3, "))        
+    }
+
+    func testRemove() {
+        let marb = Marble(numPlayers: 9, lastMarble: 15)
+        for _ in 0...3 {
+            marb.currentMarble += 1
+            marb.insert()
+            marb.incrPC(by:2)
+        }
+        marb.decrPC(by: 2)
+        marb.remove()
+        let result = printCircle(circle: marb.circle, withCount: marb.circleCount)
+        XCTAssertEqual(test: "testRemove result", withExpression: (result == "0, 2, 1, 3, "))        
+    }
+
+    func testPlaceNextMarble() {
+        var result = ""
+        for data in testData {
+            let marb = Marble(numPlayers: data.0, lastMarble: data.1)
+            for _ in 0..<marb.lastMarble {
+                marb.placeNextMarble()
+                if data == (9, 25, 32) {
+                    result = printCircle(circle: marb.circle, withCount: marb.circleCount)
+                }
+            }
+            let max = marb.player.max() ?? 0
+            if data == (9, 25, 32) {
+                XCTAssertEqual(test: "testPlaceMarble result", withExpression: (result == "0, 16, 8, 17, 4, 18, 19, 2, 24, 20, 25, 10, 21, 5, 22, 11, 1, 12, 6, 13, 3, 14, 7, 15, "))
+            }
+            XCTAssertEqual(test: "testPlaceMarble \(data)", withExpression: (max == data.2))
+        }
+    }
+
+    func day09Tests() {
+        testMarbleInit()
+        testInsert()
+        testRemove()
+        testPlaceNextMarble()
+    }
+
+    func day09Final() {
+        var marb = Marble(numPlayers: 477, lastMarble: 70851)
+        for _ in 0..<marb.lastMarble {
+            marb.placeNextMarble()
+        }
+        var max = marb.player.max() ?? 0
+        print("Answer to part 1 is: \(max)")
+        marb = Marble(numPlayers: 477, lastMarble: 7085100)
+        for i in 0..<marb.lastMarble {
+            marb.placeNextMarble()
+            if i % 1000000 == 0 { print("\(i)")}
+        }
+        max = marb.player.max() ?? 0
+        print("Answer to part 2 is: \(max)")
+    }
+}
+
+
diff --git a/Sources/AOC2018/main.swift b/Sources/AOC2018/main.swift
index ace17ec..66a77f2 100644
--- a/Sources/AOC2018/main.swift
+++ b/Sources/AOC2018/main.swift
@@ -20,6 +20,7 @@ allTests.append(Day05().tests)
 allTests.append(Day06().tests)
 allTests.append(Day07().tests)
 allTests.append(Day08().tests)
+allTests.append(Day09().tests)
 
 // Compile list of Answers
 allFinal.append(Day01().final)
@@ -30,6 +31,7 @@ allFinal.append(Day05().final)
 allFinal.append(Day06().final)
 allFinal.append(Day07().final)
 allFinal.append(Day08().final)
+allFinal.append(Day09().final)
 
 if onlyOneDay > 0 {
     print("\nDay \(onlyOneDay)")