'ion-option' is not a known element

<ion-item>
  <ion-label>Hair Color</ion-label>
  <ion-select value="brown" ok-text="Okay" cancel-text="Dismiss">
    <ion-select-option value="brown">Brown</ion-select-option>
    <ion-select-option value="blonde">Blonde</ion-select-option>
    <ion-select-option value="black">Black</ion-select-option>
    <ion-select-option value="red">Red</ion-select-option>
  </ion-select>
</ion-item>

ionic 4 has changed its syntax.

Use 'ion-option' instead of 'ion-select-option'.

<ion-item>
  <ion-label>Gender</ion-label>
  <ion-select [(ngModel)]="this.gender">
    <ion-option value="f">Female</ion-option>
    <ion-option value="m">Male</ion-option>
  </ion-select>
</ion-item>

It works for me as expected. Thank You

I used below code and got it working. Ionic 4

 <ion-item>
      <ion-select value="brown" ok-text="Okay" cancel-text="Dismiss">
      <ion-select-option value="brown">Brown</ion-select-option>
      <ion-select-option value="blonde">Blonde</ion-select-option>
      <ion-select-option value="black">Black</ion-select-option>
      <ion-select-option value="red">Red</ion-select-option>
    </ion-select>
</ion-item>