diff --git a/.idea/compiler.xml b/.idea/compiler.xml
new file mode 100644
index 0000000..b86273d
--- /dev/null
+++ b/.idea/compiler.xml
@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="CompilerConfiguration">
+    <bytecodeTargetLevel target="21" />
+  </component>
+</project>
\ No newline at end of file
diff --git a/.idea/deploymentTargetSelector.xml b/.idea/deploymentTargetSelector.xml
new file mode 100644
index 0000000..b268ef3
--- /dev/null
+++ b/.idea/deploymentTargetSelector.xml
@@ -0,0 +1,10 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="deploymentTargetSelector">
+    <selectionStates>
+      <SelectionState runConfigName="app">
+        <option name="selectionMode" value="DROPDOWN" />
+      </SelectionState>
+    </selectionStates>
+  </component>
+</project>
\ No newline at end of file
diff --git a/app/build.gradle.kts b/app/build.gradle.kts
index bf7a1c7..9ba7386 100644
--- a/app/build.gradle.kts
+++ b/app/build.gradle.kts
@@ -46,5 +46,6 @@ dependencies {
     implementation(libs.credentials.play.services.auth)
     implementation(libs.googleid)
     implementation(libs.firebase.database)
+    implementation(libs.activity)
 }
 
diff --git a/app/src/main/AndroidManifest.xml b/app/src/main/AndroidManifest.xml
index 551e598..d16227a 100644
--- a/app/src/main/AndroidManifest.xml
+++ b/app/src/main/AndroidManifest.xml
@@ -1,25 +1,37 @@
-<?xml version="1.0" encoding="utf-8"?>
-<manifest xmlns:android="http://schemas.android.com/apk/res/android"
-    xmlns:tools="http://schemas.android.com/tools">
-
-    <application
-        android:allowBackup="true"
-        android:dataExtractionRules="@xml/data_extraction_rules"
-        android:fullBackupContent="@xml/backup_rules"
-        android:icon="@mipmap/ic_launcher"
-        android:label="@string/app_name"
-        android:roundIcon="@mipmap/ic_launcher_round"
-        android:supportsRtl="true"
-        android:theme="@style/Theme.SmartAgenda">
-        <activity
-            android:name=".MainActivity"
-            android:exported="true">
-            <intent-filter>
-                <action android:name="android.intent.action.MAIN" />
-
-                <category android:name="android.intent.category.LAUNCHER" />
-            </intent-filter>
-        </activity>
-    </application>
-
-</manifest>
\ No newline at end of file
+<?xml version="1.0" encoding="utf-8"?>
+<manifest xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:tools="http://schemas.android.com/tools">
+
+    <application
+        android:allowBackup="true"
+        android:dataExtractionRules="@xml/data_extraction_rules"
+        android:fullBackupContent="@xml/backup_rules"
+        android:icon="@mipmap/ic_launcher"
+        android:label="@string/app_name"
+        android:roundIcon="@mipmap/ic_launcher_round"
+        android:supportsRtl="true"
+        android:theme="@style/Theme.SmartAgenda">
+
+        <!-- LOGIN como Activity inicial -->
+        <activity
+            android:name=".Login"
+            android:exported="true">
+            <intent-filter>
+                <action android:name="android.intent.action.MAIN" />
+                <category android:name="android.intent.category.LAUNCHER" />
+            </intent-filter>
+        </activity>
+
+        <!-- Registo -->
+        <activity
+            android:name=".Registro"
+            android:exported="false" />
+
+        <!-- MainActivity (apenas acessível depois do login) -->
+        <activity
+            android:name=".MainActivity"
+            android:exported="false" />
+
+    </application>
+
+</manifest>
diff --git a/app/src/main/java/com/example/smartagenda/ui/Login.java b/app/src/main/java/com/example/smartagenda/ui/Login.java
new file mode 100644
index 0000000..13c3362
--- /dev/null
+++ b/app/src/main/java/com/example/smartagenda/ui/Login.java
@@ -0,0 +1,56 @@
+package com.example.smartagenda;
+
+import android.content.Intent;
+import android.os.Bundle;
+import android.widget.Button;
+import android.widget.EditText;
+import android.widget.Toast;
+
+import androidx.appcompat.app.AppCompatActivity;
+
+import com.google.firebase.auth.FirebaseAuth;
+
+public class Login extends AppCompatActivity {
+
+    private EditText campoEmail, campoPassword;
+    private Button btnEntrar, btnIrParaRegisto;
+
+    private FirebaseAuth auth;
+
+    @Override
+    protected void onCreate(Bundle savedInstanceState) {
+        super.onCreate(savedInstanceState);
+        setContentView(R.layout.activity_login);
+
+        campoEmail = findViewById(R.id.campoEmail);
+        campoPassword = findViewById(R.id.campoPassword);
+        btnEntrar = findViewById(R.id.btnEntrar);
+        btnIrParaRegisto = findViewById(R.id.btnIrParaRegisto);
+
+        auth = FirebaseAuth.getInstance();
+
+        btnEntrar.setOnClickListener(v -> {
+            String email = campoEmail.getText().toString();
+            String password = campoPassword.getText().toString();
+
+            if (email.isEmpty() || password.isEmpty()) {
+                Toast.makeText(this, "Preencha todos os campos!", Toast.LENGTH_SHORT).show();
+                return;
+            }
+
+            auth.signInWithEmailAndPassword(email, password)
+                    .addOnSuccessListener(aVoid -> {
+                        Toast.makeText(this, "Login efetuado!", Toast.LENGTH_SHORT).show();
+                        startActivity(new Intent(this, MainActivity.class));
+                        finish();
+                    })
+                    .addOnFailureListener(e ->
+                            Toast.makeText(this, "Erro: " + e.getMessage(), Toast.LENGTH_LONG).show()
+                    );
+        });
+
+        btnIrParaRegisto.setOnClickListener(v ->
+                startActivity(new Intent(this, Registro.class))
+        );
+    }
+}
diff --git a/app/src/main/java/com/example/smartagenda/ui/Registro.java b/app/src/main/java/com/example/smartagenda/ui/Registro.java
new file mode 100644
index 0000000..2e2d9e1
--- /dev/null
+++ b/app/src/main/java/com/example/smartagenda/ui/Registro.java
@@ -0,0 +1,52 @@
+package com.example.smartagenda;
+
+import android.content.Intent;
+import android.os.Bundle;
+import android.widget.Button;
+import android.widget.EditText;
+import android.widget.Toast;
+
+import androidx.appcompat.app.AppCompatActivity;
+
+import com.google.firebase.auth.FirebaseAuth;
+
+public class Registro extends AppCompatActivity {
+
+    private EditText campoEmail, campoPassword;
+    private Button btnCriarConta;
+
+    private FirebaseAuth auth;
+
+    @Override
+    protected void onCreate(Bundle savedInstanceState) {
+        super.onCreate(savedInstanceState);
+        setContentView(R.layout.activity_registro);
+
+        campoEmail = findViewById(R.id.campoEmailRegisto);
+        campoPassword = findViewById(R.id.campoPasswordRegisto);
+        btnCriarConta = findViewById(R.id.btnCriarConta);
+
+        auth = FirebaseAuth.getInstance();
+
+        btnCriarConta.setOnClickListener(v -> {
+
+            String email = campoEmail.getText().toString();
+            String password = campoPassword.getText().toString();
+
+            if (email.isEmpty() || password.isEmpty()) {
+                Toast.makeText(this, "Preencha todos os campos!", Toast.LENGTH_SHORT).show();
+                return;
+            }
+
+            auth.createUserWithEmailAndPassword(email, password)
+                    .addOnSuccessListener(aVoid -> {
+                        Toast.makeText(this, "Conta criada!", Toast.LENGTH_SHORT).show();
+                        startActivity(new Intent(this, Login.class));
+                        finish();
+                    })
+                    .addOnFailureListener(e ->
+                            Toast.makeText(this, "Erro: " + e.getMessage(), Toast.LENGTH_LONG).show()
+                    );
+        });
+    }
+}
diff --git a/app/src/main/res/drawable/rounded_edittext.xml b/app/src/main/res/drawable/rounded_edittext.xml
new file mode 100644
index 0000000..f6f5593
--- /dev/null
+++ b/app/src/main/res/drawable/rounded_edittext.xml
@@ -0,0 +1,7 @@
+<?xml version="1.0" encoding="utf-8"?>
+<shape xmlns:android="http://schemas.android.com/apk/res/android"
+    android:shape="rectangle">
+    <solid android:color="#F2F2F2"/>
+    <corners android:radius="12dp"/>
+    <padding android:left="8dp" android:top="8dp" android:right="8dp" android:bottom="8dp"/>
+</shape>
diff --git a/app/src/main/res/layout/activity_login.xml b/app/src/main/res/layout/activity_login.xml
new file mode 100644
index 0000000..2949760
--- /dev/null
+++ b/app/src/main/res/layout/activity_login.xml
@@ -0,0 +1,10 @@
+<?xml version="1.0" encoding="utf-8"?>
+<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
+    xmlns:tools="http://schemas.android.com/tools"
+    android:id="@+id/main"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent"
+    tools:context=".ui.Login">
+
+</androidx.constraintlayout.widget.ConstraintLayout>
\ No newline at end of file
diff --git a/app/src/main/res/layout/activity_registro.xml b/app/src/main/res/layout/activity_registro.xml
new file mode 100644
index 0000000..22499dc
--- /dev/null
+++ b/app/src/main/res/layout/activity_registro.xml
@@ -0,0 +1,60 @@
+<?xml version="1.0" encoding="utf-8"?>
+<ScrollView xmlns:android="http://schemas.android.com/apk/res/android"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent"
+    android:padding="24dp"
+    android:background="#FFFFFF">
+
+    <LinearLayout
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:orientation="vertical"
+        android:gravity="center">
+
+        <ImageView
+            android:layout_width="120dp"
+            android:layout_height="120dp"
+            android:src="@drawable/ic_launcher_foreground"
+            android:layout_marginBottom="24dp"/>
+
+        <EditText
+            android:id="@+id/nome"
+            android:layout_width="match_parent"
+            android:layout_height="50dp"
+            android:hint="Nome completo"
+            android:background="@drawable/rounded_edittext"
+            android:padding="12dp"
+            android:layout_marginBottom="16dp"/>
+
+        <EditText
+            android:id="@+id/email"
+            android:layout_width="match_parent"
+            android:layout_height="50dp"
+            android:hint="Email"
+            android:background="@drawable/rounded_edittext"
+            android:padding="12dp"
+            android:inputType="textEmailAddress"
+            android:layout_marginBottom="16dp"/>
+
+        <EditText
+            android:id="@+id/password"
+            android:layout_width="match_parent"
+            android:layout_height="50dp"
+            android:hint="Password"
+            android:background="@drawable/rounded_edittext"
+            android:padding="12dp"
+            android:inputType="textPassword"
+            android:layout_marginBottom="16dp"/>
+
+        <Button
+            android:id="@+id/btnRegistar"
+            android:layout_width="match_parent"
+            android:layout_height="50dp"
+            android:text="Criar Conta"
+            android:textColor="#FFFFFF"
+            android:textSize="18sp"
+            android:backgroundTint="#000000"
+            android:layout_marginTop="8dp"/>
+
+    </LinearLayout>
+</ScrollView>