diff --git a/modules/freakoutBidAdapter.js b/modules/freakoutBidAdapter.js
new file mode 100644
index 00000000000..698bd7378fe
--- /dev/null
+++ b/modules/freakoutBidAdapter.js
@@ -0,0 +1,179 @@
+import {registerBidder} from '../src/adapters/bidderFactory.js';
+import {isEmpty} from '../src/utils.js';
+import {BANNER, NATIVE, VIDEO} from '../src/mediaTypes.js';
+import {config} from '../src/config.js';
+import {tryAppendQueryString} from '../libraries/urlUtils/urlUtils.js';
+
+const BIDDER_CODE = 'freakout';
+const ENDPOINT = 'https://ad.rfp.fout.jp/ad';
+const ADAPTER_VERSION = '1.0.0';
+
+export const spec = {
+  code: BIDDER_CODE,
+  supportedMediaTypes: [BANNER, VIDEO, NATIVE],
+
+  /**
+   * Determines whether the given bid request is valid.
+   *
+   * @param {BidRequest} bid The bid params to validate.
+   * @return boolean True if this is a valid bid, and false otherwise.
+   */
+  isBidRequestValid: function (bid) {
+    return !!(bid.params.adspot_id);
+  },
+
+  /**
+   * Make a server request from the list of BidRequests.
+   *
+   * @param {BidRequest[]} validBidRequests - an array of bids
+   * @param {*} bidderRequest
+   * @return {ServerRequest[]} Info describing the request to the server.
+   */
+  buildRequests: function (validBidRequests, bidderRequest) {
+    const serverRequests = [];
+
+    let endpointUrl = config.getConfig(`${BIDDER_CODE}.endpoint_url`);
+
+    for (let i = 0; i < validBidRequests.length; i++) {
+      const req = validBidRequests[i];
+
+      let query = '';
+      query = tryAppendQueryString(query, 'adspot_id', req.params.adspot_id);
+      query = tryAppendQueryString(query, 'ad_type', req.params.ad_type);
+      query = tryAppendQueryString(query, 'media_url', bidderRequest.refererInfo.referer);
+      query = tryAppendQueryString(query, 'hb', 'prebidjs');
+      query = tryAppendQueryString(query, 'pb_ver', '$prebid.version$');
+      query = tryAppendQueryString(query, 'pb_adapter_ver', ADAPTER_VERSION);
+      query = tryAppendQueryString(query, 'pb_tid', req.ortb2Imp?.ext?.tid);
+      query = tryAppendQueryString(query, 'pb_bid', req.bidId);
+      query = tryAppendQueryString(query, 'cur', getCurrency());
+      query = tryAppendQueryString(query, 'sizes', getSizes(req));
+
+      serverRequests.push({
+        method: 'GET',
+        url: endpointUrl || ENDPOINT,
+        data: query,
+        adspotId: req.params.adspot_id
+      });
+    }
+
+    return serverRequests;
+  },
+
+  /**
+   * Unpack the response from the server into a list of bids.
+   *
+   * @param {ServerResponse} serverResponse A successful response from the server.
+   * @param {ServerRequest} serverRequest
+   * @return {Array<Object>} An array of bids which were nested inside the server.
+   */
+  interpretResponse: function (serverResponse, serverRequest) {
+    const body = serverResponse.body;
+    if (isEmpty(body)) {
+      return [];
+    }
+
+    const adspotId = serverRequest.adspotId;
+
+    const ad = body.items[0];
+    const creative = makeCreative(adspotId, body);
+
+    const bid = {
+      requestId: ad.pb_bid,
+      cpm: Number(ad.cpm),
+      currency: ad.cur,
+      width: Number(ad.creative_width),
+      height: Number(ad.creative_height),
+      ad: creative,
+      ttl: Number(ad.ttl) || 300,
+      creativeId: ad.creative_id,
+      netRevenue: true,
+    };
+    if (ad.vast_xml) {
+      bid.vastXml = ad.vast_xml;
+    }
+
+    return [bid];
+  },
+
+  /**
+   * Register the user sync pixels which should be dropped after the auction.
+   *
+   * @param {SyncOptions} syncOptions Which user syncs are allowed?
+   * @param {ServerResponse[]} serverResponses List of server's responses.
+   * @return {UserSync[]} The user syncs which should be dropped.
+   */
+  getUserSyncs: function (syncOptions, serverResponses) {
+    const syncs = [];
+
+    if (serverResponses.length === 0) {
+      return syncs;
+    }
+
+    serverResponses.forEach(res => {
+      const body = res.body;
+      if (syncOptions.pixelEnabled && Array.isArray(body.sync_urls)) {
+        body.sync_urls.forEach(url => {
+          syncs.push({
+            type: 'image',
+            url: url
+          })
+        });
+      }
+      if (syncOptions.iframeEnabled && Array.isArray(body.sync_iframe_urls)) {
+        body.sync_iframe_urls.forEach(url => {
+          syncs.push({
+            type: 'iframe',
+            url: url
+          })
+        });
+      }
+    });
+
+    return syncs;
+  }
+};
+
+/**
+ * @param {BidRequest} req
+ * @return {string|null}
+ */
+function getSizes(req) {
+  /** @type {string[][]|undefined} */
+  const sizes = req.sizes;
+  if (!sizes || sizes.length < 1) return null;
+  return sizes.filter(x => x.length === 2)
+    .map(x => `${x[0]}x${x[1]}`)
+    .join(',');
+}
+
+/**
+ * @return {string} USD or JPY
+ */
+function getCurrency() {
+  if (config.getConfig('currency.adServerCurrency') &&
+    config.getConfig('currency.adServerCurrency').toUpperCase() === 'USD') {
+    return 'USD';
+  }
+  return 'JPY';
+}
+
+/**
+ * @param {string} adspotId
+ * @param {*} body
+ */
+function makeCreative(adspotId, body) {
+  return `<div><ins data-rfp-display-adspot-id="${adspotId}"></ins></div>` +
+    `<script id="rfp-ad-response-${adspotId}" type="application/json">${safeJSONString(JSON.stringify(body))}</script>` +
+    `<script src="https://js.rfp.fout.jp/rfp-display.js"></script>` +
+    `<script>RFP.Display.Default.lazyLoading(document.querySelector("[data-rfp-display-adspot-id=${adspotId}]").parentElement, {offline:true})</script>`;
+}
+
+function safeJSONString(s) {
+  return s.replace(/&/g, '\\u0026')
+    .replace(/>/g, '\\u003e')
+    .replace(/</g, '\\u003c')
+    .replace(/'/g, '\\u0027');
+}
+
+registerBidder(spec);
diff --git a/modules/freakoutBidAdapter.md b/modules/freakoutBidAdapter.md
new file mode 100644
index 00000000000..9f0c984d86a
--- /dev/null
+++ b/modules/freakoutBidAdapter.md
@@ -0,0 +1,39 @@
+# Overview
+
+```
+Module Name: FreakOut Bid Adapter
+Module Type: Bidder Adapter
+Maintainer:  rfp-tech@fout.jp
+```
+
+# Description
+
+Connects to FreakOut exchange for bids.
+
+FreakOut bid adapter supports Banner.
+
+# Test Parameters
+```
+var adUnits = [
+    // Banner adUnit
+    {
+        code: 'test-div',
+        mediaTypes: {
+            banner: {
+                sizes: [
+                    [300, 250],
+                    [320, 50],
+                    [320, 100]
+                ]
+            }
+        },
+        bids: [{
+            bidder: 'freakout',
+            params: {
+                adspot_id: 'NDgxOjUx',
+                ad_type: 14
+            }
+        }]
+    }
+];
+```
diff --git a/test/spec/modules/freakoutBidAdapter_spec.js b/test/spec/modules/freakoutBidAdapter_spec.js
new file mode 100644
index 00000000000..a54706a8021
--- /dev/null
+++ b/test/spec/modules/freakoutBidAdapter_spec.js
@@ -0,0 +1,184 @@
+import {spec} from 'modules/freakoutBidAdapter.js';
+import {newBidder} from 'src/adapters/bidderFactory.js';
+import prebid from '../../../package.json';
+
+const ENDPOINT = 'https://ad.rfp.fout.jp/ad';
+const ADAPTER_VERSION = '1.0.0';
+
+describe('FreakOutAdapter', function () {
+  const adapter = newBidder(spec);
+
+  describe('inherited functions', function () {
+    it('exists and is a function', function () {
+      expect(adapter.callBids).to.exist.and.to.be.a('function');
+    });
+  });
+
+  describe('isBidRequestValid', function () {
+    let bid = {
+      bidder: 'freakout',
+      params: {
+        adspot_id: 'ABCD1234',
+        ad_type: 14
+      }
+    };
+
+    it('should return true when required params found', function () {
+      expect(spec.isBidRequestValid(bid)).to.be.true;
+    });
+
+    it('should return false when required params are not passed', function () {
+      let bid = Object.assign({}, bid);
+      delete bid.params;
+      bid.params = {};
+      expect(spec.isBidRequestValid(bid)).to.be.false;
+    });
+  });
+
+  describe('buildRequests', function () {
+    const bidRequests = [
+      {
+        bidder: 'freakout',
+        params: {
+          adspot_id: 'ABCD1234',
+          ad_type: 14
+        },
+        adUnitCode: 'adunit-code',
+        sizes: [
+          [300, 250],
+          [320, 50],
+          [320, 100],
+        ],
+        bidId: '2b84475b5b636e',
+        bidderRequestId: '1f4001782ac16c',
+        auctionId: 'aba03555-4802-4c45-9f15-05ffa8594cff',
+        ortb2Imp: {
+          ext: {
+            tid: '791e9d84-af92-4903-94da-24c7426d9d0c',
+          }
+        }
+      },
+    ];
+
+    it('sends bid request to ENDPOINT via GET', function () {
+      const bidderRequest = {
+        refererInfo: {
+          referer: 'https://example.com',
+        },
+      };
+
+      const requests = spec.buildRequests(bidRequests, bidderRequest);
+      expect(requests[0].url).to.equal(ENDPOINT);
+      expect(requests[0].method).to.equal('GET');
+      expect(requests[0].data).to.equal(`adspot_id=ABCD1234&ad_type=14&media_url=https%3A%2F%2Fexample.com&hb=prebidjs&pb_ver=${prebid.version}&pb_adapter_ver=${ADAPTER_VERSION}&pb_tid=791e9d84-af92-4903-94da-24c7426d9d0c&pb_bid=2b84475b5b636e&cur=JPY&sizes=300x250%2C320x50%2C320x100&`);
+    });
+  });
+
+  describe('interpretResponse', function () {
+    const bidderRequests = [
+      {
+        bidder: 'freakout',
+        params: {
+          adspot_id: 'ABCD1234',
+          ad_type: 14
+        },
+        adUnitCode: 'adunit-code',
+        sizes: [
+          [300, 250],
+          [320, 50],
+          [320, 100],
+        ],
+        bidId: '2b84475b5b636e',
+        bidderRequestId: '1f4001782ac16c',
+        auctionId: 'aba03555-4802-4c45-9f15-05ffa8594cff',
+        transactionId: '791e9d84-af92-4903-94da-24c7426d9d0c',
+      }
+    ];
+
+    it('should get correct banner bid response', function () {
+      const response = {
+        sync_urls: [
+          'https://sync.example.com/1.html',
+          'https://sync.example.com/2.html',
+        ],
+        sync_iframe_urls: [
+          'https://sync.example.com/3.html',
+          'https://sync.example.com/4.html',
+        ],
+        items: [
+          {
+            creative_id: 'creative-1',
+            creative_html: '<div></div>',
+            creative_width: '300',
+            creative_height: '250',
+            ttl: 200,
+            cpm: 30,
+            cur: 'JPY',
+            pb_bid: '2b84475b5b636e',
+          },
+        ],
+      };
+
+      const expectedResponse = {
+        // ad: '<div></div>',
+        cpm: 30,
+        creativeId: 'creative-1',
+        currency: 'JPY',
+        height: 250,
+        netRevenue: true,
+        requestId: '2b84475b5b636e',
+        ttl: 200,
+        width: 300,
+      };
+
+      const result = spec.interpretResponse({body: response}, bidderRequests);
+      expect(result).to.have.lengthOf(1);
+      expect(result[0]).to.include(expectedResponse);
+      expect(result[0].ad).to.be.a('string');
+    });
+
+    it('handles no bid responses', function () {
+      const response = '';
+
+      const result = spec.interpretResponse({body: response}, bidderRequests);
+      expect(result).to.have.lengthOf(0);
+    });
+  });
+
+  describe('getUserSyncs', function () {
+    const bidResponse = {
+      body: {
+        sync_urls: [
+          'https://sync1.example.com',
+          'https://sync2.example.com',
+        ],
+        sync_iframe_urls: [
+          'https://sync3.example.com',
+          'https://sync4.example.com',
+        ],
+      },
+    };
+
+    it('should return pixel syncs', function () {
+      const syncs = spec.getUserSyncs({pixelEnabled: true, iframeEnabled: true}, [bidResponse]);
+      expect(syncs).to.deep.equal([
+        {
+          type: 'image',
+          url: 'https://sync1.example.com',
+        },
+        {
+          type: 'image',
+          url: 'https://sync2.example.com',
+        },
+        {
+          type: 'iframe',
+          url: 'https://sync3.example.com',
+        },
+        {
+          type: 'iframe',
+          url: 'https://sync4.example.com',
+        },
+      ]);
+    });
+  })
+});