diff --git a/lib/frenzy/approved_client.ex b/lib/frenzy/approved_client.ex
new file mode 100644
index 0000000..456fcb2
--- /dev/null
+++ b/lib/frenzy/approved_client.ex
@@ -0,0 +1,21 @@
+defmodule Frenzy.ApprovedClient do
+  use Ecto.Schema
+  import Ecto.Changeset
+
+  schema "approved_clients" do
+    field :client_id, :string
+    field :auth_code, :string
+    field :access_token, :string
+
+    belongs_to :user, Frenzy.User
+
+    timestamps()
+  end
+
+  @doc false
+  def changeset(approved_client, attrs) do
+    approved_client
+    |> cast(attrs, [:client_id, :auth_code, :access_token])
+    |> validate_required([:client_id])
+  end
+end
diff --git a/lib/frenzy/fervor_client.ex b/lib/frenzy/fervor_client.ex
new file mode 100644
index 0000000..08e6b1d
--- /dev/null
+++ b/lib/frenzy/fervor_client.ex
@@ -0,0 +1,31 @@
+defmodule Frenzy.FervorClient do
+  use Ecto.Schema
+  import Ecto.Changeset
+
+  def to_fervor(client) do
+    %{
+      client_name: client.client_name,
+      website: client.website,
+      redirect_uri: client.redirect_uri,
+      client_id: client.client_id,
+      client_secret: client.client_secret
+    }
+  end
+
+  schema "fervor_clients" do
+    field :client_name, :string
+    field :website, :string
+    field :redirect_uri, :string
+    field :client_id, :string
+    field :client_secret, :string
+
+    timestamps()
+  end
+
+  @doc false
+  def changeset(client, attrs) do
+    client
+    |> cast(attrs, [:client_name, :website, :redirect_uri, :client_id, :client_secret])
+    |> validate_required([:client_name, :redirect_uri, :client_id, :client_secret])
+  end
+end
diff --git a/lib/frenzy/user.ex b/lib/frenzy/user.ex
index 5a09bc1..9b06b0b 100644
--- a/lib/frenzy/user.ex
+++ b/lib/frenzy/user.ex
@@ -9,6 +9,8 @@ defmodule Frenzy.User do
     field :fever_password, :string, virtual: true
     field :fever_auth_token, :string
 
+    has_many :approved_clients, Frenzy.ApprovedClient, on_delete: :delete_all
+
     has_many :groups, Frenzy.Group, on_delete: :delete_all
 
     timestamps()
diff --git a/lib/frenzy_web/controllers/fervor_controller.ex b/lib/frenzy_web/controllers/fervor_controller.ex
new file mode 100644
index 0000000..e55a5c5
--- /dev/null
+++ b/lib/frenzy_web/controllers/fervor_controller.ex
@@ -0,0 +1,30 @@
+defmodule FrenzyWeb.FervorController do
+  use FrenzyWeb, :controller
+  alias Frenzy.{Repo, FervorClient, Group, Feed, Filter, Item}
+  alias FrenzyWeb.Router.Helpers, as: Routes
+  alias FrenzyWeb.Endpoint
+  import Ecto.Query
+
+  plug Plug.Parsers, parsers: [:urlencoded, :multipart]
+
+  def register(conn, _params) do
+    %{"client_name" => client_name, "redirect_uri" => redirect_uri} = conn.body_params
+    website = Map.get(conn.body_params, "website")
+
+    changeset =
+      FervorClient.changeset(
+        %FervorClient{},
+        %{
+          "client_name" => client_name,
+          "website" => website,
+          "redirect_uri" => redirect_uri,
+          "client_id" => :crypto.strong_rand_bytes(32) |> Base.url_encode64(padding: false),
+          "client_secret" => :crypto.strong_rand_bytes(32) |> Base.url_encode64(padding: false)
+        }
+      )
+
+    {:ok, client} = Repo.insert(changeset)
+
+    json(conn, FervorClient.to_fervor(client))
+  end
+end
diff --git a/lib/frenzy_web/controllers/login_controller.ex b/lib/frenzy_web/controllers/login_controller.ex
index a201f96..5a7f6c4 100644
--- a/lib/frenzy_web/controllers/login_controller.ex
+++ b/lib/frenzy_web/controllers/login_controller.ex
@@ -5,22 +5,24 @@ defmodule FrenzyWeb.LoginController do
   alias FrenzyWeb.Endpoint
   import Ecto.Query
 
-  def login(conn, _params) do
-    render(conn, "login.html")
+  def login(conn, params) do
+    render(conn, "login.html", %{
+      continue: Map.get(params, "continue")
+    })
   end
 
   @error_message "Invalid username or password"
 
-  def login_post(conn, %{"username" => username, "password" => password}) do
+  def login_post(conn, %{"username" => username, "password" => password} = params) do
     user = Repo.get_by(User, username: username)
 
     case Bcrypt.check_pass(user, password) do
       {:ok, user} ->
         user_token = Phoenix.Token.sign(Endpoint, "user token", user.id)
+        conn = put_session(conn, :user_token, user_token)
 
-        conn
-        |> put_session(:user_token, user_token)
-        |> redirect(to: Routes.group_path(Endpoint, :index))
+        redirect_uri = Map.get(params, "continue") || Routes.group_path(Endpoint, :index)
+        redirect(conn, to: redirect_uri)
 
       {:error, _reason} ->
         conn
diff --git a/lib/frenzy_web/controllers/oauth_controller.ex b/lib/frenzy_web/controllers/oauth_controller.ex
new file mode 100644
index 0000000..296d220
--- /dev/null
+++ b/lib/frenzy_web/controllers/oauth_controller.ex
@@ -0,0 +1,191 @@
+defmodule FrenzyWeb.OauthController do
+  use FrenzyWeb, :controller
+  alias Frenzy.{Repo, FervorClient, User, ApprovedClient}
+  alias FrenzyWeb.Router.Helpers, as: Routes
+  alias FrenzyWeb.Endpoint
+
+  def authorize_get(conn, params) do
+    user_token = get_session(conn, :user_token)
+
+    case Phoenix.Token.verify(Endpoint, "user token", user_token, max_age: 24 * 60 * 60) do
+      {:error, _reason} ->
+        continue = "#{conn.request_path}?#{conn.query_string}"
+        redirect(conn, to: Routes.login_path(Endpoint, :login, continue: continue))
+
+      {:ok, user_id} ->
+        case Repo.get(User, user_id) do
+          nil ->
+            continue = "#{conn.request_path}?#{conn.query_string}"
+            redirect(conn, to: Routes.login_path(Endpoint, :login, continue: continue))
+
+          user ->
+            conn
+            |> assign(:user, user)
+            |> try_render_authorize(params)
+        end
+    end
+  end
+
+  def try_render_authorize(
+        conn,
+        %{
+          "response_type" => "code",
+          "client_id" => client_id,
+          "redirect_uri" => redirect_uri
+        } = params
+      ) do
+    case Repo.get_by(FervorClient, client_id: client_id) do
+      nil ->
+        conn
+
+      client ->
+        if redirect_uri == client.redirect_uri do
+          render(conn, "authorize.html", %{
+            client: client,
+            state: Map.get(params, "state")
+          })
+        else
+          conn
+          |> put_status(400)
+          |> json(%{error: "mismatched redirect uri"})
+        end
+    end
+  end
+
+  def try_render_authorize(conn, _params) do
+    conn
+    |> put_status(400)
+    |> json(%{error: "invalid parameters"})
+  end
+
+  def authorize_post(conn, params) do
+    user_token = get_session(conn, :user_token)
+
+    case Phoenix.Token.verify(Endpoint, "user token", user_token, max_age: 24 * 60 * 60) do
+      {:error, _reason} ->
+        continue = "#{conn.request_path}?#{conn.query_string}"
+        redirect(conn, to: Routes.login_path(Endpoint, :login, continue: continue))
+
+      {:ok, user_id} ->
+        case Repo.get(User, user_id) do
+          nil ->
+            continue = "#{conn.request_path}?#{conn.query_string}"
+            redirect(conn, to: Routes.login_path(Endpoint, :login, continue: continue))
+
+          user ->
+            conn
+            |> assign(:user, user)
+            |> try_authorize(params)
+        end
+    end
+  end
+
+  def try_authorize(conn, %{"client_id" => client_id} = params) do
+    user = conn.assigns[:user]
+    client = Repo.get_by(FervorClient, client_id: client_id)
+
+    state = Map.get(params, "state")
+
+    auth_code = :crypto.strong_rand_bytes(32) |> Base.url_encode64(padding: false)
+
+    changeset =
+      Ecto.build_assoc(user, :approved_clients, %{
+        auth_code: auth_code,
+        client_id: client_id
+      })
+
+    {:ok, _approved_client} = Repo.insert(changeset)
+
+    case client.redirect_uri do
+      "urn:ietf:wg:oauth:2.0:oob" ->
+        render(conn, "successfully_authorized.html", %{
+          auth_code: auth_code
+        })
+
+      redirect_uri ->
+        parsed = URI.parse(redirect_uri)
+
+        query =
+          URI.encode_query(
+            if state, do: %{code: auth_code, state: state}, else: %{code: auth_code}
+          )
+
+        uri = %URI{parsed | query: query}
+        redirect(conn, to: uri)
+    end
+  end
+
+  def try_authorize(conn, _params) do
+    conn
+    |> put_status(400)
+    |> json(%{error: "invalid parameters"})
+  end
+
+  def token(
+        conn,
+        %{
+          "redirect_uri" => redirect_uri,
+          "client_id" => client_id,
+          "client_secret" => client_secret
+        } = params
+      ) do
+    case Repo.get_by(FervorClient, client_id: client_id) do
+      nil ->
+        conn
+        |> put_status(401)
+        |> json(%{error: "invalid_client", error_description: "incorrect client information"})
+
+      client ->
+        if client_secret == client.client_secret and redirect_uri == client.redirect_uri do
+          conn
+          |> assign(:client, client)
+          |> try_generate_token(params)
+        else
+          conn
+          |> put_status(400)
+          |> json(%{error: "invalid_grant", error_description: "incorrect client information"})
+        end
+    end
+  end
+
+  def token(conn, _params) do
+    json(conn, %{error: "invalid_request", error_description: "missing parameters"})
+  end
+
+  def try_generate_token(conn, %{
+        "grant_type" => "authorization_code",
+        "authorization_code" => auth_code
+      }) do
+    case Repo.get_by(ApprovedClient, auth_code: auth_code) do
+      nil ->
+        conn
+        |> put_status(400)
+        |> json(%{error: "invalid_grant", error_description: "invalid authorization code"})
+
+      approved_client ->
+        access_token = :crypto.strong_rand_bytes(32) |> Base.url_encode64(padding: false)
+
+        changeset =
+          ApprovedClient.changeset(approved_client, %{
+            auth_code: nil,
+            access_token: access_token
+          })
+
+        {:ok, _approved_client} = Repo.update(changeset)
+
+        json(conn, %{
+          access_token: access_token,
+          token_type: "bearer"
+        })
+    end
+  end
+
+  def try_generate_token(conn, _params) do
+    conn
+    |> put_status(400)
+    |> json(%{
+      error: "unsupported_grant_type",
+      error_description: "only grant_type=authorization_code is supported"
+    })
+  end
+end
diff --git a/lib/frenzy_web/router.ex b/lib/frenzy_web/router.ex
index d9d7d14..2e97382 100644
--- a/lib/frenzy_web/router.ex
+++ b/lib/frenzy_web/router.ex
@@ -10,11 +10,6 @@ defmodule FrenzyWeb.Router do
   end
 
   pipeline :authenticate do
-    # plug :accepts, ["html"]
-    # plug :fetch_session
-    # plug :fetch_flash
-    # plug :protect_from_forgery
-    # plug :put_secure_browser_headers
     plug FrenzyWeb.Plug.Authenticate
   end
 
@@ -59,8 +54,18 @@ defmodule FrenzyWeb.Router do
     post "/api/fever.php", FeverController, :post
   end
 
-  # Other scopes may use custom stacks.
-  # scope "/api", FrenzyWeb do
-  #   pipe_through :api
-  # end
+  scope "/", FrenzyWeb do
+    pipe_through :api
+
+    post "/api/v1/register", FervorController, :register
+
+    post "/oauth/token", OauthController, :token
+  end
+
+  scope "/", FrenzyWeb do
+    pipe_through :browser
+
+    get "/oauth/authorize", OauthController, :authorize_get
+    post "/oauth/authorize", OauthController, :authorize_post
+  end
 end
diff --git a/lib/frenzy_web/templates/login/login.html.eex b/lib/frenzy_web/templates/login/login.html.eex
index 3c61165..9cfec7c 100644
--- a/lib/frenzy_web/templates/login/login.html.eex
+++ b/lib/frenzy_web/templates/login/login.html.eex
@@ -1,6 +1,7 @@
-<% IO.inspect(get_flash(@conn, :error)) %>
-
 <%= form_tag Routes.login_path(@conn, :login_post), method: :post do %>
+  <%= if @continue do %>
+    <input type="hidden" name="continue" value="<%= @continue %>">
+  <% end %>
   <div class="form-group">
     <label for="username">Username</label>
     <input type="text" name="username" id="username">
diff --git a/lib/frenzy_web/templates/oauth/authorize.html.eex b/lib/frenzy_web/templates/oauth/authorize.html.eex
new file mode 100644
index 0000000..936c296
--- /dev/null
+++ b/lib/frenzy_web/templates/oauth/authorize.html.eex
@@ -0,0 +1,11 @@
+<h1><%= @client.client_name %> wants to access your account</h1>
+
+<%= form_tag Routes.oauth_path(@conn, :authorize_post), method: :post do %>
+  <input type="hidden" name="client_id" value="<%= @client.client_id %>">
+  <%= if @state do %>
+    <input type="hidden" name="state" value="<%= @state %>">
+  <% end %>
+  <div class="form-group">
+    <%= submit "Grant access" %>
+  </div>
+<% end %>
\ No newline at end of file
diff --git a/lib/frenzy_web/templates/oauth/successfully_authorized.html.eex b/lib/frenzy_web/templates/oauth/successfully_authorized.html.eex
new file mode 100644
index 0000000..247bca1
--- /dev/null
+++ b/lib/frenzy_web/templates/oauth/successfully_authorized.html.eex
@@ -0,0 +1,3 @@
+<h1>Authorization Successful</h1>
+<p>Authorization Code:</p>
+<pre><%= @auth_code %></pre>
\ No newline at end of file
diff --git a/lib/frenzy_web/views/oauth_view.ex b/lib/frenzy_web/views/oauth_view.ex
new file mode 100644
index 0000000..af5ad0e
--- /dev/null
+++ b/lib/frenzy_web/views/oauth_view.ex
@@ -0,0 +1,3 @@
+defmodule FrenzyWeb.OauthView do
+  use FrenzyWeb, :view
+end
diff --git a/priv/repo/migrations/20190327233837_create_fervor_clients.exs b/priv/repo/migrations/20190327233837_create_fervor_clients.exs
new file mode 100644
index 0000000..d291ed6
--- /dev/null
+++ b/priv/repo/migrations/20190327233837_create_fervor_clients.exs
@@ -0,0 +1,15 @@
+defmodule Frenzy.Repo.Migrations.CreateFervorClients do
+  use Ecto.Migration
+
+  def change do
+    create table(:fervor_clients) do
+      add :client_name, :string
+      add :website, :string
+      add :redirect_uri, :string
+      add :client_id, :string
+      add :client_secret, :string
+
+      timestamps()
+    end
+  end
+end
diff --git a/priv/repo/migrations/20190328203923_create_approved_clients.exs b/priv/repo/migrations/20190328203923_create_approved_clients.exs
new file mode 100644
index 0000000..6e7ee5e
--- /dev/null
+++ b/priv/repo/migrations/20190328203923_create_approved_clients.exs
@@ -0,0 +1,15 @@
+defmodule Frenzy.Repo.Migrations.CreateApprovedClients do
+  use Ecto.Migration
+
+  def change do
+    create table(:approved_clients) do
+      add :client_id, :string
+      add :auth_code, :string
+      add :access_token, :string
+
+      add :user_id, references(:users, on_delete: :delete_all)
+
+      timestamps()
+    end
+  end
+end